Heat Fluctuations in Brownian Transducers

Heat fluctuation probability distribution function in Brownian transducers operating between two heat reservoirs is studied. We find, both analytically and numerically, that the recently proposed Fluctuation Theorem for Heat Exchange [C. Jarzynski and D. K. Wojcik, Phys. Rev. Lett. 92, 230602 (2004)] has to be modified when the coupling mechanism between both baths is considered. We also extend such relation when external work is present. Our work fixes the domain of applicability of the theorem in more realistic operating systems.Comment: Comments are welcom

From the Two Faces of Unionism to the Facebook Society: Union Voice in a 21st Century Context, Manpower Human Resources Lab Discussion Paper No. 6

Union membership has declined precipitously in the US over the past 40 years. Can anything be done to stem this decline? This paper argues that union voice is an attribute (among others) of union membership that is experiential in nature and that unlike the costs of unionisation, can be discerned only after joining a union. This makes the act of ‘selling’ unionism to workers (and to some extent firms as well) rather difficult. Supportive social trends and social customs are required in order to make union membership’s many hard-to-observe benefits easier to discern. Most membership based institutions face the same dilemma. However, recent social networking organizations such as Facebook and other on-line communities have been rather successful in attracting millions of members in a relatively short period of time. The question of whether the union movement can appropriate some of these lessons is discussed with reference to historical and contemporary examples

Symmetric Brownian motor

In this paper we present a model of a symmetric Brownian motor (SBM) which changes the sign of its velocity when the temperature gradient is inverted. The velocity, external work and efficiency are studied as a function of the temperatures of the baths and other relevant parameters. The motor shows a current reversal when another parameter (a phase shift) is varied. Analytical predictions and results from numerical simulations are performed and agree very well. Generic properties of this type of motors are discussed.Comment: 8 pages and 10 figure

Employee voice and human resource management: an empirical analysis using British data

The definition of formal employee voice employed in this paper is a variant of the definition developed by Hirschman (1970) in his seminal monograph and later elaborated and appropriated to unions in the labour market by Freeman and Medoff (1984). What we refer to as formal voice is any institutionalised form of two-way communication between management and employees. This is not the same as information sharing or other types of one-way consultation. Meaningful two-way dialogue, as that found typically in union collective bargained voice, is what formal employee voice refers to. As we endeavour to show in this paper, these forms of two-way communication typically extend beyond union voice to non-union forms of representation and direct forms of two-way dialogue, such as problem-solving groups and the statutory systems of works council voice developed as part of deeper European Union (EU) integration. Broader definitions of voice can also be invoked for the labour market as a whole or even for society more generally. In this context see recent work by Adrian Wilkinson and his colleagues (Dundon et al., 2004) and also John Budd’s Employment with a Human Face (2004). Some may take our definition of voice above and simply state that a formal voice system is 'the way workers communicate with management'. For us that would not be a poor workable definition. But how does that play out when we talk about Human Resource Management (HRM) techniques and their role in either abetting or inhibiting voice at work? HRM is not a voice system. Instead we assert that it has a different purpose altogether but may employ voice alongside in order to achieve the end goal of improving worker performance. This assertion flies against most received wisdom and evidence from the US, where union voice (the only real form permitted by the Wagner Act) often sits uncomfortably with HR. In England, up to now, the only thorough evidence by Wood and Machin (2005) suggested no correlation between voice (union) and HRM adoption. In this paper, however, we offer a new explanation for these findings above and in the process contribute some important new findings of our own. The principal source of formal employee voice has typically been provided by trade unions. However, in Britain, where our empirical analysis resides, unions have not been the sole, or even main, conduit for worker-management voice relations for more than three decades. Since the 1960s, firms in Britain have been combining traditional collective bargaining over wages and working conditions with independent non-union channels of two-way communication. Practically, this means things like having a non-union employee-employer committee to handle health-safety issues, promotion criteria or disability concerns. In my own university, a traditional collective bargaining process has neatly resided alongside a plethora of non-union administration and staff committees that discuss nearly every aspect of day-to-day work life and even strategic university planning goals. How these varying types and intensity of voice systems at work can (and do) sit alongside certain managerial innovations for the improvement of employee productivity, is the subject matter of our paper

Tight coupling in thermal Brownian motors

We study analytically a thermal Brownian motor model and calculate exactly the Onsager coefficients. We show how the reciprocity relation holds and that the determinant of the Onsager matrix vanishes. Such condition implies that the device is built with tight coupling. This explains why Carnot's efficiency can be achieved in the limit of infinitely slow velocities. We also prove that the efficiency at maximum power has the maximum possible value, which corresponds to the Curzon-Alhborn bound. Finally, we discuss the model acting as a Brownian refrigerator

Brans-Dicke DGP Brane Cosmology

We consider a five dimensional DGP-brane scenario endowed with a non-minimally coupled scalar field within the context of Brans-Dicke theory. This theory predicts that the mass appearing in the gravitational potential is modified by the addition of the mass of the effective intrinsic curvature on the brane. We also derive the effective four dimensional field equations on a 3+1 dimensional brane where the fifth dimension is assumed to have an orbifold symmetry. Finally, we discuss the cosmological implications of this setup, predicting an accelerated expanding universe with a value of the Brans-Dicke parameter $\omega$ consistent with values resulting from the solar system observations.Comment: 12 pages, 1 figure, to appear in JCA

Lifetime Measurement of the 6s Level of Rubidium

We present a lifetime measurements of the 6s level of rubidium. We use a time-correlated single-photon counting technique on two different samples of rubidium atoms. A vapor cell with variable rubidium density and a sample of atoms confined and cooled in a magneto-optical trap. The 5P_{1/2} level serves as the resonant intermediate step for the two step excitation to the 6s level. We detect the decay of the 6s level through the cascade fluorescence of the 5P_{3/2} level at 780 nm. The two samples have different systematic effects, but we obtain consistent results that averaged give a lifetime of 45.57 +- 0.17 ns.Comment: 10 pages, 9 figure

Coarsening in potential and nonpotential models of oblique stripe patterns

We study the coarsening of two-dimensional oblique stripe patterns by numerically solving potential and nonpotential anisotropic Swift-Hohenberg equations. Close to onset, all models exhibit isotropic coarsening with a single characteristic length scale growing in time as $t^{1/2}$. Further from onset, the characteristic lengths along the preferred directions $\hat{x}$ and $\hat{y}$ grow with different exponents, close to 1/3 and 1/2, respectively. In this regime, one-dimensional dynamical scaling relations hold. We draw an analogy between this problem and Model A in a stationary, modulated external field. For deep quenches, nonpotential effects produce a complicated dislocation dynamics that can lead to either arrested or faster-than-power-law growth, depending on the model considered. In the arrested case, small isolated domains shrink down to a finite size and fail to disappear. A comparison with available experimental results of electroconvection in nematics is presented.Comment: 13 pages, 13 figures. To appear in Phys. Rev.

From weak to strong coupling of localized surface plasmons to guided modes in a luminescent slab

We investigate a periodic array of aluminum nanoantennas embedded in a light-emitting slab waveguide. By varying the waveguide thickness we demonstrate the transition from weak to strong coupling between localized surface plasmons in the nanoantennas and refractive index guided modes in the waveguide. We experimentally observe a non-trivial relationship between extinction and emission dispersion diagrams across the weak to strong coupling transition. These results have implications for a broad class of photonic structures where sources are embedded within coupled resonators. For nanoantenna arrays, strong vs. weak coupling leads to drastic modifications of radiation patterns without modifying the nanoantennas themselves, thereby representing an unprecedented design strategy for nanoscale light sources

A CO Survey of Young Planetary Nebulae

We report the results of a sensitive survey of young planetary nebulae in the CO J=2-1 line that significantly increases the available data on warm, dense, molecular gas in the early phases of planetary nebula formation. The observations were made using the IRAM 30 m telescope with the 3 by 3 pixel Heterodyne Receiver Array (HERA). The array provides an effective means of discriminating the CO emission of planetary nebulae in the galactic plane from contaminating emission of interstellar clouds along the line of sight. 110 planetary nebulae were observed in the survey and 40 were detected. The results increase the number of young planetary nebulae with known CO emission by approximately a factor of two. The CO spectra yield radial velocities for the detected nebulae, about half of which have uncertain or no velocity measurements at optical wavelengths. The CO profiles range from parabolic to double-peaked, tracing the evolution of structure in the molecular gas. The line widths are significantly larger than on the Asymptotic Giant Branch, and many of the lines show extended wings, which probably result from the effects on the envelopes of high velocity jets.Comment: 29 pages, 2 figures (with multiple panels), to be published in Astrophysical Journal Supplement Serie