Dynamical Response of Nanomechanical Oscillators in Immiscible Viscous Fluid for in vitro Biomolecular Recognition

Dynamical response of nanomechanical cantilever structures immersed in a viscous fluid is important to in vitro single-molecule force spectroscopy, biomolecular recognition of disease-specific proteins, and the detection of microscopic dynamics of proteins. Here we study the stochastic response of biofunctionalized nanomechanical cantilevers beam in a viscous fluid. Using the fluctuation-dissipation theorem we derive an exact expression for the spectral density of the displacement and a linear approximation for the resonance frequency shift. We find that in a viscous solution the frequency shift of the nanoscale cantilever is determined by surface stress generated by biomolecular interaction with negligible contributions from mass loading.Comment: 4 pages, 2 figures, RevTex4. See http://nano.bu.edu/ for related paper

Standard and derived Planck quantities: selected analysis and derivations

We provide an overview of the fundamental units of physical quantities determined naturally by the values of fundamental constants of nature. We discuss a comparison between the 'Planck units', now widely used in theoretical physics and the pre-quantum 'Stoney units' in which, instead of the Planck constant, the charge of the electron is used with very similar quantitative results. We discuss some of the physical motivation for these special units, attributed much after they were introduced, and also put forth a summary of the arguments supporting various cases for making specific physical interpretations of the meanings of some of these units. The new aspects we discuss are a possible physical basis for the Stoney units, their link to the Planck units, and also the importance of Planck units for thermodynamical quantities in the context of quantum gravity.Comment: 22 pages, 1 tabl

Cosmological Analogues of the Bartnik--McKinnon Solutions

We present a numerical classification of the spherically symmetric, static solutions to the Einstein--Yang--Mills equations with cosmological constant $\Lambda$. We find three qualitatively different classes of configurations, where the solutions in each class are characterized by the value of $\Lambda$ and the number of nodes, $n$, of the Yang--Mills amplitude. For sufficiently small, positive values of the cosmological constant, \Lambda < \Llow(n), the solutions generalize the Bartnik--McKinnon solitons, which are now surrounded by a cosmological horizon and approach the deSitter geometry in the asymptotic region. For a discrete set of values $\Lambda_{\rm reg}(n) > \Lambda_{\rm crit}(n)$, the solutions are topologically $3$--spheres, the ground state $(n=1)$ being the Einstein Universe. In the intermediate region, that is for \Llow(n) < \Lambda < \Lhig(n), there exists a discrete family of global solutions with horizon and ``finite size''.Comment: 16 pages, LaTeX, 9 Postscript figures, uses epsf.st

Trialogue on the number of fundamental constants

This paper consists of three separate articles on the number of fundamental dimensionful constants in physics. We started our debate in summer 1992 on the terrace of the famous CERN cafeteria. In the summer of 2001 we returned to the subject to find that our views still diverged and decided to explain our current positions. LBO develops the traditional approach with three constants, GV argues in favor of at most two (within superstring theory), while MJD advocates zero.Comment: Version appearing in JHEP; 31 pages late

School-based HPV vaccination positively impacts parents’ attitudes toward adolescent vaccination

Introduction This qualitative study aimed to explore parental attitudes, knowledge and decision-making about HPV vaccination for adolescents in the context of a gender-neutral school-based Australian National Immunisation Program (NIP). Methods Semi-structured interviews with parents of adolescents eligible for HPV vaccination were undertaken as part of an evaluation of a cluster-randomised controlled trial of a complex intervention in 40 schools (2013–2015). In this qualitative study, we purposively recruited a nested sample of parents from 11 schools across two Australian jurisdictions. Interviews explored parent knowledge and understanding of the HPV vaccine program; HPV vaccination decision-making; their adolescent’s knowledge about HPV vaccination; and their adolescent’s understanding about HPV vaccination, sexual awareness and behaviour. Transcripts were analysed using inductive and deductive thematic analysis. Results Parents’ of 22 adolescents had positive attitudes towards the program; the school-based delivery platform was the key driver shaping acceptance of and decision-making about HPV vaccination. They had difficulty recalling, or did not read, HPV vaccination information sent home. Some adolescents were involved in discussions about vaccination, with parents’ responsible for ultimate vaccine decision-making. All parents supported in-school education for adolescents about HPV and HPV vaccination. Parents’ knowledge about HPV vaccination was limited to cervical cancer and was largely absent regarding vaccination in males. Conclusions Parents’ positive attitudes towards the NIP and inclusion of the HPV vaccine is central to their vaccine decision-making and acceptance. More intensive communication strategies including school education opportunities are required to improve parents’ knowledge of HPV-related disease and to promote vaccine decision-making with adolescents

Variable Curvature Slab Molecular Dynamics as a Method to Determine Surface Stress

A thin plate or slab, prepared so that opposite faces have different surface stresses, will bend as a result of the stress difference. We have developed a classical molecular dynamics (MD) formulation where (similar in spirit to constant-pressure MD) the curvature of the slab enters as an additional dynamical degree of freedom. The equations of motion of the atoms have been modified according to a variable metric, and an additional equation of motion for the curvature is introduced. We demonstrate the method to Au surfaces, both clean and covered with Pb adsorbates, using many-body glue potentials. Applications to stepped surfaces, deconstruction and other surface phenomena are under study.Comment: 16 pages, 8 figures, REVTeX, submitted to Physical Review

Women We Loved: Paradoxes of public and private in the biographical television drama

Broadcast to critical acclaim and relatively large audiences for its niche channel, the Women We Loved season consisted of biographical dramatisations of three prominent female figures of 20th-century British culture. These dramas shared in common narratives that centre on the two aspects of ‘the public’ and ‘the private’: the tension between public career and personal life and the discrepancy between celebrity persona and private individual. Combining theoretical insights from feminist studies of biography with close textual analysis, this article analyses how performance, aesthetics and narrative express the ambivalent placement of their protagonists between public and private spheres

Measurement of Contractile Stress Generated by Cultured Rat Muscle on Silicon Cantilevers for Toxin Detection and Muscle Performance Enhancement

Background: To date, biological components have been incorporated into MEMS devices to create cell-based sensors and assays, motors and actuators, and pumps. Bio-MEMS technologies present a unique opportunity to study fundamental biological processes at a level unrealized with previous methods. The capability to miniaturize analytical systems enables researchers to perform multiple experiments in parallel and with a high degree of control over experimental variables for high-content screening applications.Methodology/Principal Findings: We have demonstrated a biological microelectromechanical system (BioMEMS) based on silicon cantilevers and an AFM detection system for studying the physiology and kinetics of myotubes derived from embryonic rat skeletal muscle. It was shown that it is possible to interrogate and observe muscle behavior in real time, as well as selectively stimulate the contraction of myotubes with the device. Stress generation of the tissue was estimated using a modification of Stoney's equation. Calculated stress values were in excellent agreement with previously published results for cultured myotubes, but not adult skeletal muscle. Other parameters such as time to peak tension (TPT), the time to half relaxation (KRT) were compared to the literature. It was observed that the myotubes grown on the BioMEMS device, while generating stress magnitudes comparable to those previously published, exhibited slower TPT and KRT values. However, growth in an enhanced media increased these values. From these data it was concluded that the myotubes cultured on the cantilevers were of an embryonic phenotype. The system was also shown to be responsive to the application of a toxin, veratridine.Conclusions/Significance: The device demonstrated here will provide a useful foundation for studying various aspects of muscle physiology and behavior in a controlled high-throughput manner as well as be useful for biosensor and drug discovery applications