Josephson junction array type I-V characteristics of quench-condensed ultra thin films of Bi

In this communication we report studies of d.c current-voltage (I-V) characteristics of ultra thin films of Bi, quench condensed on single crystal sapphire substrates at T = 15K. The hysteretic I-V characteristics are explained using a resistively and capacitively shunted junction (RCSJ) model of Josephson junction arrays. The Josephson coupling energy($E_J$) and the charging energy($E_c$) are calculated for different thickness($d$) values. A low resistance state is found in the low current regime below the critical current, $I_c$. This resistance $R_0$ is found to have a minimum at a particular thickness ($d_c$) value. Reflection High Energy Electron Diffraction (RHEED) studies are done on these films. A distinct appearance of a diffuse ring near $d_c$ is observed in the diffraction images, consistent with the recent STM studies(Ekinci and Valles, PRL {\bf 82}(1999) 1518). These films show an irreversible annealing when temperature is increased. The annealing temperature ($T_a$) also has a maximum at the same thickness. Althoguh the R$_s$ vs T of quench condensed Bi films suggest that the films are uniform, our results indicate that even in thick films, the order parameter is not fully developed over the complete area of the film. These results are discussed qualitatively.Comment: 6 pages, 6 figure

"Income Distribution in a Monetary Economy: A Ricardo-Keynes Synthesis"

The paper provides a novel theory of income distribution and achieves an integration of monetary and value theories along Ricardian lines, extended to a monetary production economy as understood by Keynes. In a monetary economy, capital is a fund that must be maintained. This idea is captured in the circuit of capital as first defined by Marx. We introduce the circuit of fixed capital; this circuit is closed when the present value of prospective returns from employing it is equal to its supply price. In a steady-growth equilibrium with nominal wages and interest rates given, the equation that closes the circuit of fixed capital can be solved for prices, implying a definitive income distribution. Accordingly, the imputation for fixed capital costs is equivalent to that of a money contract of equal length, which is the payment per period that will repay the cost of the fixed asset, together with interest. It follows that if capital assets remain in use for a period longer than is required to amortize them, their earnings beyond that period have an element of pure rent.Income Distribution; Circuits of Capital; Monetary Economy

Magnetic metamaterials in the blue range using aluminum nanostructures

We report an experimental and theoretical study of the optical properties of two-dimensional arrays of aluminum nanoparticle in-tandem pairs. Plasmon resonances and effective optical constants of these structures are investigated and strong magnetic response as well as negative permeability are observed down to 400 nm wavelength. Theoretical calculations based on the finite-difference time-domain method are performed for various particle dimensions and lattice parameters, and are found to be in good agreement with the experimental results. The results show that metamaterials operating across the whole visible wavelength range are feasible.Comment: 3 pages, 4 figure

Nanoelectromechanical systems

Nanoelectromechanical systems (NEMS) are drawing interest from both technical and scientific communities. These are electromechanical systems, much like microelectromechanical systems, mostly operated in their resonant modes with dimensions in the deep submicron. In this size regime, they come with extremely high fundamental resonance frequencies, diminished active masses,and tolerable force constants; the quality (Q) factors of resonance are in the range Q~10^3–10^5—significantly higher than those of electrical resonant circuits. These attributes collectively make NEMS suitable for a multitude of technological applications such as ultrafast sensors, actuators, and signal processing components. Experimentally, NEMS are expected to open up investigations of phonon mediated mechanical processes and of the quantum behavior of mesoscopic mechanical systems. However, there still exist fundamental and technological challenges to NEMS optimization. In this review we shall provide a balanced introduction to NEMS by discussing the prospects and challenges in this rapidly developing field and outline an exciting emerging application, nanoelectromechanical mass detection

Improving the Resolution and Throughput of Achromatic Talbot Lithography

High-resolution patterning of periodic structures over large areas has several applications in science and technology. One such method, based on the long-known Talbot effect observed with diffraction gratings, is achromatic Talbot lithography (ATL). This method offers many advantages over other techniques, such as high resolution, large depth of focus, high throughput, etc. Although the technique has been studied in the past, its limits have not yet been explored. Increasing the efficiency and the resolution of the method is essential and might enable many applications in science and technology. In this work, we combine this technique with spatially coherent and quasi-monochromatic light at extreme ultraviolet (EUV) wavelengths and explore new mask design schemes in order to enhance its throughput and resolution. We report on simulations of various mask designs in order to explore their efficiency. Advanced and optimized nanofabrication techniques have to be utilized to achieve high quality and efficient masks for ATL. Exposures using coherent EUV radiation from the Swiss light source (SLS) have been performed, pushing the resolution limits of the technique for dense hole or dot patterning down to 40 nm pitch. In addition, through extensive simulations, alternative mask designs with rings instead of holes are explored for the efficient patterning of hole/dot arrays. We show that these rings exhibit similar aerial images to hole arrays, while enabling higher efficiency and thereby increased throughput for ATL exposures. The mask designs with rings show that they are less prone to problems associated with pattern collapse during the nanofabrication process and therefore are promising for achieving higher resolution

Generalized Knudsen number for unsteady fluid flow

We explore the scaling behavior of an unsteady flow that is generated by an oscillating body of finite size in a gas. If the gas is gradually rarefied, the Navier-Stokes equations begin to fail and a kinetic description of the flow becomes more appropriate. The failure of the Navier-Stokes equations can be thought to take place via two different physical mechanisms: either the continuum hypothesis breaks down as a result of a finite size effect or local equilibrium is violated due to the high rate of strain. By independently tuning the relevant linear dimension and the frequency of the oscillating body, we can experimentally observe these two different physical mechanisms. All the experimental data, however, can be collapsed using a single dimensionless scaling parameter that combines the relevant linear dimension and the frequency of the body. This proposed Knudsen number for an unsteady flow is rooted in a fundamental symmetry principle, namely, Galilean invariance

Some New Integral Inequalities for Several Kinds of Convex Functions

In this study, we obtain some new integral inequalities for different classes of convex functions by using some elementary inequalities and classical inequalities like general Cauchy inequality and Minkowski inequality