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.     

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.     

An assessment instrument for identifying counseling needs of elementary-aged students: The multimodal sentence completion form for children (MSCF-C)

This article discusses the use of a sentence completion instrument predicated on Lazarus' multimodal system. The instrument, entitled The Multimodal Sentence Completion Form for Chindren (MSCF-C), is designed to systematically assess client needs and assist in identifying intervention strategies. Administration procedures and profile development also are addressed. To assist the reader in understanding the strengths and limitations of the MSCF-C, a case study of a 12-year-old sixth-grade student is presented. Based on the verbatim responses of this student, a profile of client characteristics and plausible strategies was outlined.     

How Arizona Community College Teachers Learn to Teach

A survey of novice community college teachers in Arizona examined what learning experiences are available to help them learn to teach, and how valuable they consider those experiences to be in learning to teach. These activities can be organized into four general categories: reflective activities, classroom application, formal methods of learning teaching strategies, and college-based activities. Of these activities, new teachers value reflective activities the most, followed by classroom application, then formal methods of learning teaching strategies. College-based activities got the lowest ranking. These rankings raise two questions that warrant further professional exchange and research. First, are college-based professional development activities actually less valuable in promoting student success, or are they simply perceived that way by faculty members? Second, is there an intuitive process that new teachers use to learn to teach that relies more heavily on reflective and applied activities?     

Pastoral Care: Past,Present and Future

Chris Watkins was a member of the first NAPCE executive in 1982, and has continued on that committee and on the London committee ever since. He was chair of NAPCE from 1992 to 1994, and is currently chair of the Publications Committee. He has been a maths teacher in a large secondary school, a teacher in charge of a unit for pupils whose effect on school was disruptive, and a trained school counsellor.

He is now head of the academic group ‘Assessment, Guidance and Effective Learning’ at the University of London Institute of Education, where his current areas of work include school behaviour, mentoring, tutoring, personal–social education – all centrally linked to effective learning in classrooms and school. He is course tutor to the MA in Effective Learning and the MA in School Development, and is involved in consultancy to schools and training others in consultation. Current research projects include ‘The Violence-resilient School’ and ‘Learning about Learning’.     

Electroosmotic flow in vapor deposited silicon dioxide and nitride microchannels

Electroosmotic flow was studied in thin film microchannels with silicon dioxide and silicon nitride sidewalls formed using plasma-enhanced chemical vapor deposition (PECVD). A sacrificial etching process was employed for channel fabrication allowing for cross-sections with heights of 3 μm, ranging from 2 μm to 50 μm in width. Flow rates were measured for single channels and multichannel electroosmotic pump structures for pH levels ranging from 2.6 to 8.3, and zeta potentials were calculated for both silicon dioxide and silicon nitride surfaces. Flow rates as high as 0.086 μL∕min were measured for nitride multichannel pumps at applied electric fields of 300 V∕mm. The surface characteristics of PECVD nitride were analyzed and compared to more well-known oxide surfaces to determine the density of amine sites compared to silanol sites.     

Visions of International Scientific Cooperation: The Case of Oceanic Science, 1920–1955

This work explores the attitudes of American scientists towardsinternational scientific activity, with particular respect to theoceanic sciences, during the three decades after the First WorldWar. In the mid-1950s, the Eisenhower Administration favouredthe thesis that increased international collaboration wouldstrengthen the Free World, ease Cold War tensions, and promotethe growth of science. This essay analyses elements in thatthesis, namely, scientific chauvinism, humanitarianism, andscientific interdependence. The narrative traces these themesthrough key episodes in the history of international cooperationin oceanic science, revealing how this experience shapedstrategies and expectations for cooperative scientific research.