10,909 research outputs found
Electroweak phase transition in technicolor
Several phenomenologically viable walking technicolor models have been
proposed recently. I demonstrate that these models can have first order
electroweak phase transitions, which are sufficiently strong for electroweak
baryogenesis. Strong dynamics can also lead to several separate transitions at
the electroweak scale, with the possibility of a temporary restoration and an
extra breaking of the electroweak symmetry. First order phase transitions will
produce gravitational waves, which may be detectable at future experiments.Comment: 6 pages, 4 figures. Talk at PASCOS 2010 conference, Valencia, 19-23
July 201
ON IMPROVING ECONOMETRIC ANALYSES OF GENERIC ADVERTISING IMPACTS
It is possible to obtain robust estimates of structural parameters using observational data, but it is difficult to do so. Necessary, but not sufficient, conditions are to adopt a modeling philosophy and to undertake a comprehensive evaluation of the results. Using a general-to-specific modeling philosophy, we obtained stable estimates of the long-run advertising elasticity for fluid milk. This result contrasts with an earlier, published model which did not provide stable estimates as new data points became available. It is difficult, however, to apply the general-to-specific modeling approach because it requires the researcher to specify an initial general model. But analysts are unlikely to agree on this initial model, and if this is true, then the "generality" of the model is in question. Moreover, it is a fact that the quality of the available data is sometimes insufficient to obtain the desired stable estimates.Marketing,
Simulations of solar cell absorption enhancement using resonant modes of a nanosphere array
We propose an approach for enhancing the absorption of thin-film amorphous silicon solar cells using periodic arrangements of resonant dielectric nanospheres deposited as a continuous film on top of a thin planar cell. We numerically demonstrate this enhancement using 3D full field finite difference time domain simulations and 3D finite element device physics simulations of a nanosphere array above a thin-film amorphous silicon solar cell structure featuring back reflector and anti-reflection coating. In addition, we use the full field finite difference time domain results as input to finite element device physics simulations to demonstrate that the enhanced absorption contributes to the current extracted from the device. We study the influence of a multi-sized array of spheres, compare spheres and domes and propose an analytical model based on the temporal coupled mode theory
Minnesota Agricultural Economist 689
Livestock Production/Industries, Marketing,
Fluctuations and Pinch-Offs Observed in Viscous Fingering
Our experiments on viscous (Saffman-Taylor) fingering in Hele-Shaw channels
reveal several phenomena that were not observed in previous experiments. At low
flow rates, growing fingers undergo width fluctuations that intermittently
narrow the finger as they evolve. The magnitude of these fluctuations is
proportional to Ca^{-0.64}, where Ca is the capillary number, which is
proportional to the finger velocity. This relation holds for all aspect ratios
studied up to the onset of tip instabilities. At higher flow rates, finger
pinch-off and reconnection events are observed. These events appear to be
caused by an interaction between the actively growing finger and suppressed
fingers at the back of the channel. Both the fluctuation and pinch-off
phenomena are robust but not explained by current theory.Comment: 6 pages, 3 figures; to appear in Proceedings of the Seventh
Experimental Chaos Conferenc
Gravitational Techniwaves
We investigate the production and possible detection of gravitational waves
stemming from the electroweak phase transition in the early universe in models
of minimal walking technicolor. In particular we discuss the two possible
scenarios in which one has only one electroweak phase transition and the case
in which the technicolor dynamics allows for multiple phase transitions.Comment: 30 pages, 5 figures. v2: minor changes, references added, title
changed in journa
Size-dependent electron-hole exchange interaction in Si nanocrystals
Silicon nanocrystals with diameters ranging from [approximate]2 to 5.5 nm were formed by Si ion implantation into SiO2 followed by annealing. After passivation with deuterium, the photoluminescence (PL) spectrum at 12 K peaks at 1.60 eV and has a full width at half maximum of 0.28 eV. The emission is attributed to the recombination of quantum-confined excitons in the nanocrystals. The temperature dependence of the PL intensity and decay rate at several energies between 1.4 and 1.9 eV was determined between 12 and 300 K. The temperature dependence of the radiative decay rate was determined, and is in good agreement with a model that takes into account the energy splitting between the excitonic singlet and triplet levels due to the electron-hole exchange interaction. The exchange energy splitting increases from 8.4 meV for large nanocrystals ([approximate]5.5 nm) to 16.5 meV for small nanocrystals ([approximate]2 nm). For all nanocrystal sizes, the radiative rate from the singlet state is 300–800 times larger than the radiative rate from the triplet state
The impact of entrepreneurship education on succession in ethnic minority family firms
Purpose
– The purpose of this paper is to explore the impact that entrepreneurship education can have on succession in ethnic minority family firms that operate in the highly competitive UK economy.
Design/methodology/approach
– The paper employs a complex conceptual model of ethnic minority graduates' economic activities and outlines the possible influence that entrepreneurship education can have on succession in their family firms. An illustrative case study is presented of an ethnic minority graduate who returned to work in the family firm.
Findings
– It emerges that entrepreneurship education provision in UK HEIs is insufficiently customised to, and focused on, the specific entrepreneurial needs of graduates. Educators should take into account the complex socio‐economic and cultural differences between native and ethnic minority learning environments. Effective entrepreneurship education emerges as crucial to the survival and growth of ethnic minority family businesses in the UK and could contribute positively to ownership transfer in this type of firm.
Research limitations/implications
– The proposed theoretical model has not been empirically tested and it is only indicative of the impact that entrepreneurship education could have on succession in small ethnic minority family businesses in the UK.
Originality/value
– Although prior research has explored various aspects of ownership succession, this article focuses specifically on the impact that entrepreneurship education can have on succession in small ethnic minority family firms
The Boson peak in supercooled water
We perform extensive molecular dynamics simulations of the TIP4P/2005 model of water to investigate the origin of the Boson peak reported in experiments on supercooled water in nanoconfined pores and in hydration water around proteins. We find that the onset of the Boson peak in supercooled bulk water coincides with the crossover to a predominantly low-density-like liquid below the Widom line TW. The frequency and onset temperature of the Boson peak in our simulations of bulk water agree well with the results from experiments on nanoconfined water. Our results suggest that the Boson peak in water is not an exclusive effect of confinement. We further find that, similar to other glass-forming liquids, the vibrational modes corresponding to the Boson peak are spatially extended and are related to transverse phonons found in the parent crystal, here ice Ih.We thank S. V. Buldyrev and S. Sastry for helpful discussions. The simulations were in part performed using resources provided by the Swedish National Infrastructure for Computing (SNIC) at the NSC and HPC2N centers. LGMP, KTW and DS were supported by the Swedish Research Council. KTW is also supported by the Icelandic Research Fund through the START programme. PK acknowledges the support of National Academies Keck Future Initiatives award. HES thanks NSF Grants No. CHE0911389, No. CHE0908218, and No. CHE-1213217. (Swedish Research Council; Icelandic Research Fund through the START programme; National Academies Keck Future Initiatives award; CHE0911389 - NSF; CHE0908218 - NSF; CHE-1213217 - NSF)Published versio
Fluctuations and Pinch-Offs Observed in Viscous Fingering
Our experiments on viscous (Saffman-Taylor) fingering in Hele-Shaw channels
reveal several phenomena that were not observed in previous experiments. At low
flow rates, growing fingers undergo width fluctuations that intermittently
narrow the finger as they evolve. The magnitude of these fluctuations is
proportional to Ca^{-0.64}, where Ca is the capillary number, which is
proportional to the finger velocity. This relation holds for all aspect ratios
studied up to the onset of tip instabilities. At higher flow rates, finger
pinch-off and reconnection events are observed. These events appear to be
caused by an interaction between the actively growing finger and suppressed
fingers at the back of the channel. Both the fluctuation and pinch-off
phenomena are robust but not explained by current theory.Comment: 6 pages, 3 figures; to appear in Proceedings of the Seventh
Experimental Chaos Conferenc
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