Boston College

About: Boston College is a education organization based out in Boston, Massachusetts, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 9749 authors who have published 25406 publications receiving 1105145 citations. The organization is also known as: BC.

Unidirectional rotary motion in a molecular system

Abstract: The conversion of energy into controlled motion plays an important role in both man-made devices and biological systems. The principles of operation of conventional motors are well established, but the molecular processes used by ‘biological motors’ such as muscle fibres, flagella and cilia1,2,3,4,5,6,7,8,9 to convert chemical energy into co-ordinated movement remain poorly understood10,11,12. Although ‘brownian ratchets’13,14,15,16 are known to permit thermally activated motion in one direction only, the concept of channelling random thermal energy into controlled motion has not yet been extended to the molecular level. Here we describe a molecule that uses chemical energy to activate and bias a thermally induced isomerization reaction, and thereby achieve unidirectional intramolecular rotary motion. The motion consists of a 120° rotation around a single bond connecting a three-bladed subunit to the bulky remainder of the molecule, and unidirectional motion is achieved by reversibly introducing a tether between the two units to energetically favour one of the two possible rotation directions. Although our system does not achieve continuous and fast rotation, the design principles that we have used may prove relevant for a better understanding of biological and synthetic molecular motors producing unidirectional rotary motion.

Design, theory, and measurement of a polarization-insensitive absorber for terahertz imaging

Abstract: We present the theory, design, and realization of a polarization-insensitive metamaterial absorber for terahertz frequencies. Effective-medium theory is used to describe the absorptive properties of the metamaterial in terms of optical constants---a description that has been thus far lacking. From our theoretical approach, we construct a device that yields over 95% absorption in simulation. Our fabricated design consists of a planar single unit-cell layer of metamaterial and reaches an absorptivity of 77% at 1.145 THz.

Out of Sight But Not Out of Mind: Managing Invisible Social Identities in the Workplace

Abstract: Invisible social identities influence social interaction in distinct ways and create unique dynamics in terms of identity management. We integrate research from the sexuality, illness, and racial diversity literature, as well as the stigma, disclosure, and identity literature, to create a generalized model of invisible identity management. We focus specifically on revealing and passing strategies of identity management and conclude by discussing the implications of invisible differences for diversity research.

Relationships Between Intergroup Contact and Prejudice Among Minority and Majority Status Groups

Abstract: Considerable research has shown that greater intergroup contact corresponds with lower intergroup prejudice, yet little is known regarding how the relationships between contact and prejudice may vary for members of minority and majority status groups. The present research examined differences in contact-prejudice relationships among members of minority and majority status groups, using data from a larger meta-analytic study of the effects of intergroup contact. Results indicate that the relationships between contact and prejudice tend to be weaker among members of minority status groups than among members of majority status groups. Moreover, establishing Allport's (1954) proposed conditions for optimal intergroup contact significantly predicts stronger contact-prejudice relationships among members of majority status groups, but not among members of minority status groups. Implications of these findings for future research on contact between minority and majority status groups are discussed.

Flexural phonons and thermal transport in graphene

Abstract: We show through an exact numerical solution of the phonon Boltzmann equation that the lattice thermal conductivity of graphene is dominated by contributions from the out-of-plane or flexural phonon modes, previously thought to be negligible. We connect this unexpected result to the anomalously large density of states of flexural phonons compared to their in-plane counterparts and to a symmetry-based selection rule that significantly restricts anharmonic phonon-phonon scattering of the flexural modes. The result is found to hold in the presence of the ripples known to occur in graphene, phonon-isotopic impurity scattering, and rigidity of the flexural phonon branch arising from the long-wavelength coupling between flexural and in-plane modes. Finally, accurate inclusion of the momentum conserving Normal phonon-phonon scattering processes within the context of a full solution of the phonon Boltzmann equation are shown to be essential in accurately describing the graphene thermal conductivity, in contrast to the more commonly used relaxation time and long wavelength approximations.