We consider the evolution of a thin viscous fluid sheet subject to thermocapillary effects. Using a lubrication approximation we find, for symmetric interfacial deflections, coupled evolution equations for the interfacial profile, the streamwise component of the fluid velocity and the temperature variation along the surface. Initial temperature profiles change the initial flow field through Marangoni-induced shear stresses. These changes then lead to preferred conditions for rupture prescribed by the initial temperature distribution. We show that the time to rupture may be minimized by varying the phase difference between the initial velocity profile and the initial temperature profile. For sufficiently large temperature differences, the phase difference between the initial velocity and temperature profiles determines the rupture location.

We used molecular genetic techniques and multipoint linkage analyses to locate the gene responsible for cutaneous malignant melanoma-dysplastic nevus. We evaluated 99 relatives and 26 spouses in six families with a predisposition to melanoma. Thirty-four family members had cutaneous malignant melanoma, and 31 of these 34 also had histologically confirmed dysplastic nevi. Twenty-four family members had dysplastic nevi alone. An analysis of the cosegregation of the cutaneous malignant melanoma–dysplastic nevus trait with 26 polymorphic DNA markers on the short arm of chromosome 1 demonstrated the presence of a gene for susceptibility to melanoma. The gene was located between an anonymous DNA marker (D1S47) and the gene locus for pronatrodilatin, a commonly used reference gene (PND), in chromosome band 1p36. The odds were greater than 260,000:1 in favor of linkage at this location.

To identify the chromosomal location of a gene responsible for familial hypertrophic cardiomyopathy, we used clinical and molecular genetic techniques to evaluate the members of a large kindred. Twenty surviving and 24 deceased family members had hypertrophic cardiomyopathy; 58 surviving members were unaffected. Genetic-linkage analyses were performed with polymorphic DNA loci dispersed throughout the entire genome, to identify a locus that was inherited with hypertrophic cardiomyopathy in family members. The significance of the linkage detected between the disease locus and polymorphic loci was assessed by calculating a lod score (the logarithm of the probability of observing coinheritance of two loci, assuming that they are genetically linked, divided by the probability of detecting coinheritance if they are unlinked). A DNA locus (D14S26), previously mapped to chromosome 14 and of unknown function, was found to be coinherited with the disease in this family. No instances of recombination were observed between the locus for familial hypertrophic cardiomyopathy and D14S26, yielding a lod score of +9.37 (θ= 0). These data indicate that in this kindred, the odds are greater than 2,000,000,000:1 that the gene responsible for familial hypertrophic cardiomyopathy is located on chromosome 14 (band q1).

Part of Focus on Micro- and Nanofluidics The classical theory of electrokinetic phenomena assumes a dilute solution of point-like ions in chemical equilibrium with a surface whose double-layer voltage is of order the thermal voltage, kBT/e=25 mV. In nonlinear 'induced-charge' electrokinetic phenomena, such as ac electro-osmosis, several volts 100kBT/e are applied to the double layer, and the theory breaks down and cannot explain many observed features. We argue that, under such a large voltage, counterions 'condense' near the surface, even for dilute bulk solutions. Based on simple models, we predict that the double-layer capacitance decreases and the electro-osmotic mobility saturates at large voltages, due to steric repulsion and increased viscosity of the condensed layer, respectively. The former suffices to explain observed high-frequency flow reversal in ac electro-osmosis; the latter leads to a salt concentration dependence of induced-charge flows comparable to experiments, although a complete theory is still lacking.

This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)] , was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.

Before coming to Olin, I knew I wanted one thing with my education: I wanted to help people. I believe that empathy is a defining aspect of who I am, and I want to harness this part of me to make some sort of change (which is broad, I know). I wanted to use my time at Olin to develop and pursue my passions, or at least, discover what they are. Over my four years at Olin, I believe I have found those passions, which I can summarize into three main categories: healthcare, design, and education. The stories that define my Olin experience have characteristics of one (if not more) of these themes, which I believe will shape the way I help people after my college career. Olin has given me the tools to make a difference in these categories, which these stories capture.

During the summer leading up to my first year at Franklin W. Olin College of Engineering, Alison Black, the Assistant Dean of Student Life, contacted all the incoming first-year students and requested that we each write a Statement of Interest that outlined what we wanted to accomplish when we got to Olin. My Statement of Interest outlined one dozen goals, eight of which are listed below: 1. Get Involved with leadership activities or student government 2. Help plan and organize school events 3. Volunteer with individuals with developmental disabilities 4. Work or volunteer with children 5. Take classes in business or management 6. Work on assistive technology 7. Have an internship ever summer (not always with the same company) 8. Get accepted into graduate school As I sat down to reflect on my Olin experience, I realized that much of it was summarized in the list above. I can honestly say that, with a few caveats, I reached and often exceeded all of the goals I outlined before I set foot on Olin’s Campus. In addition to reaching all of these goals, they all focused on a central theme: Engineering for Others. Below I break down the eight goals listed above and reflect on my experiences and how they all contributed to this central theme.

For as long as I can remember, I’ve found pleasure in making things. Things that moved, things that flashed, things that buzzed, things that whirred all have excited me to no end. I remember one of my first “inventions” was a handheld fan powered by an old electric toothbrush motor and a 9v battery. At the time, I did not understand the interworkings of the motor I was using, nor the chemistry of the battery, nor even how the shape of the propeller allowed it to move air. I did, however, understand what each piece did, and I found great pleasure in putting the pieces together to make something new. As I moved from grade school to junior high to high school, my knowledge of how things work grew, and with it grew my desire to make more things. When learning about kinematics in physics, my friend and I decided to build small coilguns using the circuits of discarded disposable cameras to see if the equations of motion worked out. Along the way, I unintentionally learned a lot about electricity and magnetism, RC circuits, and what a high voltage discharge across skin can feel like. Projects like this led me to be one of the founding members and vice president of my high school’s engineering club. I recognized that I not only did enjoyed making devices and contraptions, but I absorbed knowledge much more readily when I could use it to make something physical. For this reason, my choice to attend Olin College was a no-brainer. Olin’s focus on project-based learning and application driven education resonated with what I enjoyed, how I knew I absorbed information, and how I liked to apply myself. Through the whirlwind that has been my time at Olin, I have had the pleasure of taking part in many experiences that speak to the five curricular components of the Grand Challenge Scholars Program: a Grand Challenge Project, an Interdisciplinary Experience, an Entrepreneurial Experience, Global Awareness, and Service Learning. In this portfolio, I will be focusing a handful of projects and experiences that highlight these components of the program.

What drew me to Olin was the emphasis on learning through projects and experiences. Up until sixth grade, this was how I learned. In fact, the motto of my elementary school was “joyous work,” and after going to a more conventional high school that emphasized grades and test scores, I sought to return to this approach to learning. Learning through doing was surprising, challenging, and valuable for my growth as a person. Experiences that stand out are the failure of a website I tried to start for Lesbian, Gay, Bisexual and Transgendered(LGBT) students and perception-expanding experience of studying abroad in Japan. I came into these experiences not entirely prepared, but in the process I learned how much I did not know. Coming out of these experiences, I continue to learn using the skills I acquired.

My grand challenge at Olin was shaped in three main areas. Long-term research in the biology lab, interdisciplinary learning through many classes, but in particular User Oriented Collaborative Design, and participation in the campus organization Engineering Discovery. Doing research and participating in clubs in addition to classes helped me get to know others in different disciplines and learn more about their solutions to problems. Another large component of my learning involved giving and receiving feedback, both from people outside of the Olin community and within. This double dose of feedback allowed me and my teammates to better understand the problems were trying to solve. To get this feedback, many presentations were done, which gave me the confidence to stand up and present my methods and results with conviction and certainty. Many class projects were team oriented, which allowed me to learn how to work well with others. I also did work on my own with guidance in research. Doing both of these things taught me to work independently but always take others advice and criticism into account. Overall, I believe Olin provided me with an engineering education that will allow me to understand and effectively communicate with people in many disciplines with a variety of educational backgrounds.

The first twenty-five years or so of the modern successful American life has been fairly well defined by the country’s education system. Go to primary school. Get good grades. Go to college. Get good grades. Graduate with a degree in something you love. Find a good job. Make money. As a child, I was well-aware of this system. From an early age I fully intended to go to college and major in something lucrative, my thinking shaped by years of advice from parents who managed start-ups, real estate, and stocks. Well before high school I began searching for a dream, trying to decide what I should spend the rest of my life doing. I was smart. I was good at math and science. I was also good at art, theater, writing, philosophy, and other subjects that would leave me with a job that wouldn’t make the expense of college worthwhile. I also enjoyed playing Roller Coaster Tycoon. So I decided to become an engineer. Since I also grew up constantly being reminded about the virtues of running your own business, I also decided to go someplace where I could study business and entrepreneurship. This ultimately led me to Franklin W. Olin College of Engineering, a new engineering school near Boston that was on a mission to integrate entrepreneurial thought and action throughout its curriculum.

Psychologist Dan McAdams posed in a 1995 journal paper the question “what do we know when we know a person?” According to his research, there are multiple levels at which differences in personality may be described. One of them is the life story that we “[continue] to author and revise over time to make sense, for [ourselves] and others, of [our] own life in time.” (McAdams, 1995) For myself, that story takes shape somewhere around the time I’m 16 years old. I’m working in open source software communities. And I’m mistaken by one of my closest co-workers (who had not yet met me in person) for a teacher. My path since then has been shaped by a nontraditional educational institution: I’ve spent my time at Olin College of Engineering, a small school outside of Boston with the declared mission of transforming engineering education. At Olin, students engage in a largely problem-oriented, project-based curriculum and enjoy a significant amount of autonomy, allowing them to pursue their passions. These experiences have naturally shaped my relationship to my learning, which is exhibited in my narrative. As I’m about to graduate from Olin and leave this place that has made up so much of my life over the last four years behind, I want to reflect on my story in this portfolio.

A a middle school student answering the question "what do you think you'll study at college?", I was quick to cross medicine off my list. I believe my exact words were "I don't want to do anything that involves poking people." My disinterest in medicine remained largely unchallenged until I interned at Boston Device Development, a small product development consultancy in Newton, MA. As a college junior looking to develop experience in mechanical design, BDD's focus on medical devices was just the context for my work. As that summer progressed, I began to realize that medical devices are fantastic design problems becauses of their engineering challenges, human factors, and business needs. The experience reaffirmed my decision not to become a surgeon, but made me reconsider the way I viewed medicine, how innovations come to market, and how many opportunities there are to make better products. Undoubtedly it was this experience that led me to work with DePuy Synthes Mitek Sports Medicine for my senior capstone project. Our year-long project was to identify gaps in DePuys' portfolio of devices, consider the market opportunities and unmet needs of surgeons, generate new device concepts, and ultimately build a functional proof-of-concept. Because of these experiences and my hope to work on similar projects after graduation, my GCSP portfolio will focus on "Engineering better medicines."

Had you asked me why I was attending college when I first came to Olin, I likely would have answered, “Because I want to be an engineer.” Taken at face value, this would seem a reasonable answer, but my inability to better justify such an important decision just highlights my perspective at the time that college was simply a necessary step in a path to do the kind of work I thought I was interested in. Doing things because I thought it was expected of me fairly well characterized my first few semesters at Olin, be it the classes I took or the activities I engaged in. After having spent 4 years at Olin, my perspective on my education has changed radically. Rather than trying to meet external pressure, I aim to do things because they interest me. This has enabled me to explore a much broader range of topics and draw connections between a variety of fields which I otherwise would not have been exposed to. Ultimately, choosing to tailor my educational experience has led to me being far more engaged in my learning and developing significantly as a learner. Given the impact of this on me while at Olin and how I expect it to impact me after Olin, I chose to focus my GCSP portfolio on Personalized Learning.

People are more likely to improve themselves, their communities and the world if the change is simpler, more desirable, cheaper and easier than the current option, and the activation energy to switch is low. We are creatures of habit. Society has inertia. Changing the world requires changing people’s minds and altering their behaviours. My conscience compels me to try to improve my environment. Over time, I have developed my philosophy for enacting change, and refined my approach. In each of the experiences I will describe below, I identified a behaviour in my peers worth adjusting, created a desirable and simple solution to alter their actions, and gave them the tools to enact change. The scope of these experiences may not be global, but in each, my actions attempted to cause people to improve themselves as individuals, ameliorate their community or have a lesser impact on the environment. Through these, I learned how to lay the foundation for a real behavioural change in my peers, I learned how to lay the foundation for real behavioural change in my peers. This mentality scales up for Grand Challenges. The Grand Challenges cannot be resolved with technology alone, or solely through social pressures, or by simply passing a bill. They cannot be solved by throwing money at them, nor by holding hands and wishing they would go away. Grand Challenges demand all of these things together -- and more: an interconnected ecosystem of scientific innovation, an enlightened social paradigm that welcomes the change, strong political will, ample economic resources and yes, a dash of optimism. With all these elements acting in concert, we can change our behaviours in meaningful ways and be able to achieve great things.

In my GCSP portfolio, I reflect upon the connections between teaching (my lifelong calling) and my major occupations at Olin College. I describe how five roughly chronological experiences – a year-long sabbatical from my engineering degree, an inspirational education course, a series of teaching opportunities, my position as a “Resident Resource”, and numerous management positions in community organizations at Olin – correspond to five functions I believe are vital facets of an effective teacher – role model, guide, educator, mentor, and leader. For each one, I clarify my motivations and describe elements of my methodology in order to construct a set of intentions for my eventual teaching practice. The process of synthesizing this portfolio required a significant amount of introspection and self-analysis, which I understand in retrospect involved taking great strides along the path of self-awareness and personal growth. This is a journey that only grows more and more relevant with time. This portfolio serves as a collection of my actions, beliefs, goals, and realizations prior to graduation. It is a comprehensive snapshot of my professional abilities and ambitions in my early twenties.

BACKGROUND Understanding more about student decisions to leave engineering may lead to higher retention. This study builds on the literature and focuses on the experiences of a cohort of students who aimed to complete their undergraduate work in 2007. PURPOSE (HYPOTHESIS) This paper presents the outcomes of the longitudinal administration of the Persistence in Engineering survey. The goal was to identify correlates of persistence in undergraduate engineering education and professional engineering practice. DESIGN/METHOD The survey was administered seven times over four years to a cohort of students who had expressed interest in studying engineering. At the end of the study, the participants were categorized as persisters or non-persisters. Repeated measures analysis of variance was used, in conjunction with other approaches, to test for differences between the groups. RESULTS Persisters and non-persisters did not differ significantly according to the majority of the constructs. Nevertheless, parental and high school mentor influences as a motivation to study engineering, as well as confidence in math and science skills, were identified as correlates of persistence. Intention to complete an engineering major was also a correlate of persistence; it appears to decline sharply at least two semesters prior to students leaving engineering. The findings also suggest that there might be differences among non-persisters when they are further grouped by when they leave engineering. CONCLUSIONS Facilitating higher levels of mentor involvement before college might increase student motivation to study engineering, and also constitute a mechanism for fostering confidence in math and science skills. Since the intention to complete an engineering degree decreases well before students act, there may be opportunities for institutions to develop targeted interventions for students, and help them make informed decisions.

Nanofluidic technology is gaining popularity for bioanalytical applications due to advances in both nanofabrication and design. One major obstacle in the widespread adoption of such technology for bioanalytical systems is efficient detection of samples due to the inherently low analyte concentrations present in such systems. This problem is exacerbated by the push for electronic detection, which requires an even higher sensor-local sample concentration than optical detection. This paper explores one of the most common preconcentration techniques, field-amplified sample stacking, in nanofluidic systems in efforts to alleviate this obstacle. Holding the ratio of background electrolyte concentrations constant, the parameters of channel height, strength of electric field, and concentration are varied. Although in micron scale systems, these parameters have little or no effect on the final concentration enhancement achieved, nanofluidic experiments show strong dependencies on each of these parameters. Further, nanofluidic systems demonstrate an increased concentration enhancement over what is predicted and realized in microscale counterparts. Accordingly, a depth-averaged theoretical model is developed that explains these observations and furthermore predicts a novel focusing mechanism that can explain the increased concentration enhancement achieved. Specifically, when the electric double layer is sufficient in size relative to the channel height, negatively charged analyte ions are repelled from negatively charged walls, and thus prefer to inhabit the centerline of the channels. The resulting induced pressure gradients formed due to the high and low electrical conductivity fluids in the channel force the ions to move at a slower velocity in the low-conductivity region, and a faster velocity in the high-conductivity region, leading to focusing. A simple single-channel model is capable of predicting key experimental observations, while a model that incorporates the details of the fluid inlet and outlet ports allows for more detailed comparisons between model and experiment.

We studied the energetics of hover-feeding Anna's hummingbirds, using three different simultaneous techniques: heat loss as estimated via thermal imaging, metabolic rate as measured at a feeder mask using flow-through respirometry, and aerodynamic power estimated from wingbeat kinematic data. These three methods yielded comparable estimates of power output at ambient air temperatures ranging from 18 degrees to 26 degrees C, whereas heat imbalance at higher air temperatures (up to 34 degrees C) suggested loss by mechanisms other than convection and radiation from the body, such as evaporative cooling and enthalpy rise associated with exhaled air and excreted water and convective heat loss from the patagia. Hummingbirds increased wingbeat frequency and decreased stroke amplitude as air temperature increased, but overall muscle efficiency was found to be approximately constant over the experimental range of air temperatures.

We study the existence of multiple equilibrium states in a simple fluid network using Newtonian fluids and laminar flow. We demonstrate theoretically the presence of hysteresis and bistability, and we confirm these predictions in an experiment using two miscible fluids of different viscosity—sucrose solution and water. Possible applications include blood flow, microfluidics, and other network flows governed by similar principles.

Single bubble sonoluminescence (SBSL) is the brief flash of light emitted from a single, stable, acoustically forced bubble. In experiments, the maximum pressure amplitude with which a bubble may be forced is limited by considerations of spherical stability. The traditional linear stability analysis predicts a threshold for SBSL at a much lower pressure amplitude than experimental observations. This work shows that if one constructs an accurate model of the radial dynamics, the traditional linear stability analysis predicts a boundary that is in excellent agreement with experimental data.

The critical fluctuations of CuGeO3 have been measured by synchrotron x-ray scattering, and two length scales are clearly observed. The ratio between the two length scales is found to be significantly different along the a axis, with the a axis along the surface normal direction. We believe that such a directional preference is a clear sign that random surface strains, especially those caused by dislocations, are the origin of the long length scale fluctuations.

We report a neutron-scattering study of the dynamic spin correlations in Rb2MnF4, a two-dimensional spin-5/2 antiferromagnet. By tuning an external magnetic field to the value for the spin-flop line, we reduce the effective spin anisotropy to essentially zero, thereby obtaining a nearly ideal two-dimensional isotropic antiferromagnet. From the shape of the quasielastic peak as a function of temperature, we demonstrate dynamic scaling for this system and find a value for the dynamical exponent z. We compare these results to theoretical predictions for the dynamic behavior of the two-dimensional Heisenberg model, in which deviations from z=1 provide a measure of the corrections to scaling.

Helical ribbons with pitch angles of either 11° or 54° self-assemble in a wide variety of quaternary surfactant-phospholipid/fatty acid-sterol-water systems. By elastically deforming these helices, we examined their response to uniaxial forces. Under sufficient tension, a low pitch helix reversibly separates into a straight domain with a pitch angle of 90° and a helical domain with a pitch angle of 16.5°. Using a newly developed continuum elastic free energy model, we have shown that this phenomenon can be understood as a first order mechanical phase transition.

Escaping from predators often demands that animals rapidly negotiate complex environments. The smallest animals attain relatively fast speeds with high frequency leg cycling, wing flapping or body undulations, but absolute speeds are slow compared to larger animals. Instead, small animals benefit from the advantages of enhanced maneuverability in part due to scaling. Here, we report a novel behavior in small, legged runners that may facilitate their escape by disappearance from predators. We video recorded cockroaches and geckos rapidly running up an incline toward a ledge, digitized their motion and created a simple model to generalize the behavior. Both species ran rapidly at 12–15 body lengths-per-second toward the ledge without braking, dove off the ledge, attached their feet by claws like a grappling hook, and used a pendulum-like motion that can exceed one meter-per-second to swing around to an inverted position under the ledge, out of sight. We discovered geckos in Southeast Asia can execute this escape behavior in the field. Quantification of these acrobatic behaviors provides biological inspiration toward the design of small, highly mobile search-and-rescue robots that can assist us during natural and human-made disasters. We report the first steps toward this new capability in a small, hexapedal robot.