Abstract

A new method of direct, rapid nano- to micro-scale patterning of high purity cobalt is presented. The method utilizes a combination of electron beam induced deposition (EBID) and seeded growth at elevated temperatures below the temperature of spontaneous thermal decomposition. Dicobalt octacarbonyl \( \mathrm{Co_{2}(CO)_{8}}\) is used as the precursor and carbon as a seed layer. Seeded deposition is carried out in the substrate temperature range from 55 to 75°C. Deposition yield is significantly higher than conventional EBID and magnetotransport measurements indicate that resistivity, \( 22~\mu\Omega~\mathrm{cm} \), and saturation magnetization, 1.55 T, are much closer to the corresponding values for bulk Co than those for standard EBID.

Abstract

A popular method for generating micron-sized aerosols is to submerge ultrasonic ( *ω* ~ MHz) piezoelectric oscillators in a water bath. The submerged oscillator atomizes the fluid, creating droplets with radii proportional to the wavelength of the standing wave at the fluid surface. Classical theory for the Faraday instability predicts a parametric instability driving a capillary wave at the subharmonic (*ω*/2) frequency. For many applications it is desirable to reduce the size of the droplets; however, using higher frequency oscillators becomes impractical beyond a few MHz. Observations are presented that demonstrate that smaller droplets may also be created by increasing the driving amplitude of the oscillator, and that this effect becomes more pronounced for large driving frequencies. It is shown that these observations are consistent with a transition from droplets associated with subharmonic ( *ω*/2) capillary waves to harmonic (*ω*) capillary waves induced by larger driving frequencies and amplitudes, as predicted by a stability analysis of the capillary waves.

Abstract

Being able to distinguish light-quark jets from gluon jets on an event-by-event basis could significantly enhance the reach for many new physics searches at the Large Hadron Collider. Through an exhaustive search of existing and novel jet substructure observables, we find that a multivariate approach can filter out over 95% of the gluon jets while keeping more than half of the light-quark jets. Moreover, a combination of two simple variables, the charge track multiplicity and the \( p_T \)-weighted linear radial moment (girth), can achieve similar results. Our study is only Monte Carlo based, so other observables constructed using different jet sizes and parameters are used to highlight areas that deserve further theoretical and experimental scrutiny. Additional information, including distributions of around 10 000 variables, can be found at http://jets.physics.harvard.edu/qvg/.

Abstract

The role of petal spurs and specialized pollinator interactions has been studied since Darwin. Aquilegia petal spurs exhibit striking size and shape diversity, correlated with specialized pollinators ranging from bees to hawkmoths in a textbook example of adaptive radiation. Despite the evolutionary significance of spur length, remarkably little is known about Aquilegia spur morphogenesis and its evolution. Using experimental measurements, both at tissue and cellular levels, combined with numerical modelling, we have investigated the relative roles of cell divisions and cell shape in determining the morphology of the Aquilegia petal spur. Contrary to decades-old hypotheses implicating a discrete meristematic zone as the driver of spur growth, we find that Aquilegia petal spurs develop via anisotropic cell expansion. Furthermore, changes in cell anisotropy account for 99 per cent of the spur-length variation in the genus, suggesting that the true evolutionary innovation underlying the rapid radiation of Aquilegia was the mechanism of tuning cell shape.

Abstract

We demonstrate the operation of a device that can produce chitosan nanoparticles in a tunable size range from 50–300 nm with small size dispersion. A piezoelectric oscillator operated at megahertz frequencies is used to aerosolize a solution containing dissolved chitosan. The solvent is then evaporated from the aerosolized droplets in a heat pipe, leaving monodisperse nanoparticles to be collected. The nanoparticle size is controlled both by the concentration of the dissolved polymer and by the size of the aerosol droplets that are created. Our device can be used with any polymer or polymer/therapeutic combination that can be prepared in a homogeneous solution and vaporized.

From the Cover…

.. epigraph:: “Helliwell achieves a rare clarity. For instance, the derivation of the standard kinematic results starting from Einstein's postulates is outstandingly clear. Throughout he shows an unusual and sympathetic appreciation of the problems that are faced by the beginning student.” -- John Taylor, University of Colorado .. epigraph:: “*Special Relativity* is definitely much better than the books I have read on this topic, and I would recommend it to any instructor who plans to teach a course on this topic. For anyone teaching special relativity as a part of a Modern Physics course, this book offers valuable supplementary reading.” -- Shirvel Stanislaus, Valparaiso University

Abstract

A new class of observables is introduced which aims to characterize the superstructure of an event, that is, features, such as color flow, which are not determined by the jet four-momenta alone. Traditionally, an event is described as having jets which are independent objects; each jet has some energy, size, and possible substructure such as subjets or heavy flavor content. This description discards information connecting the jets to each other, which can be used to determine if the jets came from decay of a color- singlet object, or if they were initiated by quarks or gluons. An example superstructure variable, pull, is presented as a simple handle on color flow. It can be used on an event-by-event basis as a tool for distinguishing previously irreducible backgrounds at the Tevatron and the LHC.

From the Cover…

.. epigraph:: “Townsend has written an excellent book that someone needed to write for the modern physics textbook market. He has given it the same care that he gave to his excellent quantum mechanics book.” -- Jeff Dunham, Middlebury College .. epigraph:: “When I read this book I immediately adopted it for my sophomore modern physics class. This is the best introduction to quantum mechanics available.” -- B. Paul Padley, Rice University

Recent Publications

Student authorFaculty author    

71.

L. M. Belova, James C. Eckert, J. J. L. Mulders, C. Christophersen, E. D. Dahlberg, and A. Riazanova

Rapid electron beam assisted patterning of pure cobalt at elevated temperatures via seeded growth

Nanotechnology 22 (2011) 145305.
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72.

Andrew P. Higginbotham, Andrew J. Bernoff, Aaron M. Guillen, Thomas D. Donnelly, and Nathan Jones

Evidence of the harmonic Faraday instability in ultrasonic atomization experiments with a deep, inviscid fluid

Journal of the Acoustical Society of America 130 (2011) 2694-2699.
PDF document
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73.

Donna Phu, Lindsay S. Wray, Robert V. Warren, Richard Campbell Haskell, and Elizabeth Orwin

Effect of Substrate Composition and Alignment on Corneal Cell Phenotype

Tissue Engineering A 17 (2011) 799–807.
74.

Jason Gallicchio and Matthew D Schwartz

Pure samples of quark and gluon jets at the LHC

Journal of High Energy Physics 2011 (2011) .
75.

Jason Gallicchio and Matthew D Schwartz

Quark and Gluon Tagging at the LHC

Physical Review Letters 107 (2011) 172001.
PDF document
Eye candy
76.

Joshua R. Puzey, Sharon Gerbode, Scott A. Hodges, Elena M. Kramer, and L. Mahadevan

Evolution of spur-length diversity in Aquilegia petals is achieved solely through cell-shape anisotropy

Proceedings of the Royal Society B 279 (2011) 1640-1645.
PDF document
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77.

Andrew P. Higginbotham, Thomas D. Donnelly, Shenda M. Baker, and Ian K. Wright

Generation of Nanoparticles of Controlled Size Using Ultrasonic Piezoelectric Oscillators in Solution

ACS Applied Materials and Interfaces 2 (2010) 2360-2364.
PDF document
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78.

Thomas McCaffree Helliwell

Special Relativity

University Science Books, Sausalito, 2010.
Eye candy
79.

Jason Gallicchio and Matthew D. Schwartz

Seeing in Color: Jet Superstructure

Physical Review Letters 105 (2010) 022001.
PDF document
Eye candy
80.

John S. Townsend

Quantum Physics: a Fundamental Approach to Modern Physics

University Science Books, Sausalito, 2010.
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