Two-dimensional spatial manipulation of microparticles in continuous flows in acoustofluidic systems

We report a modeling and experimental study of techniques to acoustically focus particles flowing through a microfluidic channel. Our theoretical model differs from prior works in that we solve an approximate 2-D wave transmission model that accounts for wave propagation in both the solid and fluid phases. Our simulations indicate that particles can be effectively focused at driving frequencies as high as 10% off of the resonant condition. This conclusion is supported by experiments on the acoustic focusing of particles in nearly square microchannels, which are studied for different flow rates, driving frequencies and placements of the lead zirconate titanate transducer, either underneath the microchannel or underneath a parallel trough. The relative acoustic potential energy and the resultant velocity fields for particles with positive acoustic contrast coefficients are estimated in the 2-D limit. Confocal microscopy was used to observe the spatial distribution of the flowing microparticles in three dimensions. Through these studies, we show that a single driving frequency from a single piezoelectric actuator can induce the 2-D concentration of particles in a microchannel with a nearly square cross section, and we correlate these behaviors with theoretical predictions. We also show that it is possible to control the extent of focusing of the microparticles, and that it is possible to decouple the focusing of microparticles in the vertical direction from the lateral direction in rectangular channels with anisotropic cross sections. This study provides guidelines to design and operate microchip-based acoustofluidic devices for precise control over the spatial arrangement of microparticles for applications such as flow cytometry and cellular sorting.     

STRATEGIES TO EXPAND A PENPAL PROGRAM FROM SIMPLE LETTERS INTO A FULL INTERGENERATIONAL EXPERIENCE

The Senior Pen Pal Program offered in the first grade classroom at Mulready Elementary School in Hudson, MAis an example of a successful intergenerational program. The program has evolved from a letter exchange to include the assignment of books about senior citizens, regular correspondence, and structured group visits between participants. Some of the seniors visit the classroom and lead activities. The senior center is visited by the students and an intergenerational concert is held during the holidays.     

A Phrase Well Turned: Creative Facility in Narrative Production

It is commonly recognized that messages are simultaneously patterned and creative, but studies of message production have tended to focus on repetitive features of messages, to the relative exclusion of examination of their novel characteristics. This study is concerned with creative facility—the ability readily to construct novel, appropriate messages. In order to investigate this phenomenon, subjects produced a series of simple SITUATION-ACTION-BECAUSE narratives and also completed measures of speed of information processing (Digit-Symbol Substitution Test, DSST), cognitive tempo (Matching Familiar Figures Test, MFFT), and need for cognitive structure (Personal Need for Structure scale, PNS). Results indicate each of these measures was related to the speed with which participants were able to formulate their narratives. Moreover, the impact of both cognitive tempo, assessed as number of errors on the MFFT, and need for cognitive structure was heightened under more cognitively demanding message-production conditions. Implications of these results and suggestions for future research are discussed.     

Gender differences in educational attainment: Influences of the family environment

There are gender differences in educational attainment amongst British children and there is evidence that these differences emerge early in life. In this study we investigate whether boys’ and girls’ early educational attainment levels are similarly related to disadvantage in the family environment. This study uses survey data from the Millennium Cohort Study linked with the teachers Foundation Stage Profile assessment for children in the primary year of school in England between 2005 and 2006. The study finds lower attainment in communication, language and literacy and mathematical development for both boys and girls in families experiencing socio‐economic disadvantage. Early motherhood, low maternal qualifications, low family income and unemployment most strongly predict lower scores. Tests for gender interaction shows boys in families where mothers are young, where they lack qualifications or if they are living in poor quality areas are more disadvantaged compared to girls in similar circumstances.     

Effects of year-round schooling on disadvantaged students and the distribution of standardized test performance

Using detailed longitudinal data for the state of California, this paper estimates the effect of year-round school calendars on nationally standardized test performance of traditionally disadvantaged students. The student subgroups studied in this paper are: low socioeconomic status, limited English proficiency, Hispanic and Latino, and African American students. I find significant negative effects of multi-track year-round calendars on academic achievement for all subgroups examined, with only the limited English proficiency student subgroup producing unreliable estimates. Negative and significant results for another type of year-round calendar, single-track, are also found for the full sample of students and low socioeconomic status students.     

Computing and the social organization of academic work

This article discusses the academic computing movement during the 1980s. We focus on the Faculty Workstations Project at Brown University, where major computing initiatives were undertaken during the 1980s. Six departments are compared: chemistry, cognitive and linguistic sciences, geology, music, neural science, and sociology. We discuss the theoretical implications of our study for conceptualizing the relationship of computing to academic work.An early version of this article was originally published as: Technological Innovation in Higher Education: A Case Study in Academic Computing. In Morell, J. and Fleischer, M. (Eds.), (1991),Advances in the Implementation and Impact of Computer Systems, Vol. 1, JAI Press, Greenwich, Connecticut, pp. 183–209.