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INTRODUCTION The wide use of state-of-the art mass-spectrometry methods with soft ionization, such as electrospray ionization (ESI), atmospheric pressure chemical ionization (ACPI), and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, results [...], A novel derivatization method for the analysis of primary amines by MALDI mass spectrometry is proposed. Tris(2,6-dimethoxyphenyl) methyl carbenium cation reacts smoothly with primary amines, forming permanently charged adducts with the mass increment +359 Da and absorbance in the UV region. The approach was tested on a number of amines, including biologically active compounds and therapeutic agents. Keywords: trityl cation, derivatization, amines, MALDI mass spectrometry

Results of low-temperature (LT) characterizations of local rf properties of passive superconducting (SC) microwave devices are reported. A new Laser Scanning Microscope (LSM) is used.

We report on the fabrication of highly transparent superconductor/normal metal/two-dimensional electron gas junctions formed by a superconducting NbN electrode, a thin (10 nm) Au interlayer, and a two-dimensional electron gas in an InGaAs/InP heterostructure. High junction transparency has been achieved by exploiting developed process of Au/NbN evaporation and rapid annealing at 400 °C. This allowed us to observe a decrease in the differential resistance with pronounced double-dip structure within the superconducting energy gap in superconductor/two-dimensional electron gas (2DEG) proximity systems. The effect of a magnetic field perpendicular to the plane of the 2DEG on the differential resistance of the interface was studied. It has been found that the reduced subgap resistance remains in high magnetic fields. Zero-field data are analyzed within the previously established quasiclassical model for the proximity effect. [ABSTRACT FROM AUTHOR]

Different imaging modes of low temperature laser scanning microscopy (LTLSM) are used for probing local optical and superconducting properties, as well as the spatial variations in thermoelectric and electronic transport in a Y[Ba.sub.2][Cu.sub.3][O.sub.6.95]/LaAl[O.sub.3] (YBCO/LAO) superconducting microstrip resonator with micron-range resolution. The results have shown the direct spatial correlation between nonlinearity (NL) microwave and dc electronic transport properties of the YBCO film that are imposed by the twin-domain topology of the LAO substrate.

Low-temperature laser scanning microscopy (LSM) technique applied to image guided motion of vortices in patterned high-[T.sub.c] films revealed guidance of vortices by artificial microholes. It is proved that vortices are steered between antidots into a priori chosen direction by imaging of resistive photoresponse with a spatial resolution down to about 1 mum.

The operation of a toggle flip top with zero-geometrical inductance of the fluxon storage loop is simulated. The simulations show that the parametric inductance of the Pi-junction and its normal resistance R(Sub n) form a low-pass filter, which sets the low limit for Pi-junctions I(Sub c)(Super pi)R(Sub n) product, but offers a wide range of variations of the other parameters.

We have found that the size of some rapid single-flux quantum (RSFQ) logic cells based on conventional 0-type Josephson junctions can be significantly reduced by using a π-type junction as a phase shifter in passive (nonswitching) mode. In comparison with the recently suggested active (switching) π-junctions mode, the passive mode offers much greater operation margins for their critical current I[sub c][sup π]. This gives π-junctions a chance to be implemented in RSFQ designs in the near future. As an example, we have simulated the operation of a toggle flip flop with zero-geometrical inductance of the fluxon storage loop. Simulations show that the parametric inductance of the π-junction and its normal resistance R[sub n] form a low-pass filter, which sets the low limit for π-junctions I[sub c][sup π]R[sub n] product, but offers a wide range of variations of the other parameters. The possible reduction of RSFQ cell size by using π-junctions opens the way to scale superconducting logic circuits down to the submicron dimensions. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: The improvement of the coherence times of superconducting qubits depends on the reduction of the dielectric losses in the insulating materials implemented for the device fabrication. These losses depend on the density of spurious dipoles of different nature (two-level systems, TLSs) which couple to phase qubits and, hence, limit their coherence times. Hydrogenated amorphous silicon (a-Si:H), because of its lower loss tangent (tan δ) among conventional dielectrics (a-SiO, a-SiO2, a-SiNx:H), is considered as the best amorphous dielectric for superconducting qubit application. We have developed a reliable method for the direct measurement of dielectric losses in amorphous dielectric thin films using a novel design based on four lumped superconducting LC resonators connected in series without coupling capacitors. The losses are obtained as tan δ = 1/Q0, where Q0 is the intrinsic quality factor of the resonator, measured at 3dB above the resonance frequency without any fitting procedure. The series type LC resonators with a-Si:H as dielectric were fabricated by the Nb technology. The measurements were done at the conditions of a qubit application (0.5 -10GHz frequency range and low temperatures). The low values of the loss tangent of a-Si:H (up to 2.5 x 10−5 at 4.2K) have required the development of superconducting housing for the resonators in order to eliminate a spurious dependence of tan δ on the microwave power, by reducing losses which were not originated in the dielectric itself. The results of the simulations agree well with the experiments. [Copyright &y& Elsevier]

Statistical properties of continued fractions for numbers a/b, where a and b lie in the sector a, b ≥ 1, a2 + b2 ≤ R2, are studied. The main result is an asymptotic formula with two meaning terms for the quantity where sx(a/b) = ¦{j ε {1, ..., s}: [0; tj, ..., ts] ≤ x}¦ is the Gaussian statistic for the fraction a/b = [t0; t1, ..., ts]. Bibliography: 12 titles. [ABSTRACT FROM AUTHOR]

Vortices occur naturally in a wide range of gases and fluids, from macroscopic to microscopic scales. In Bose-Einstein condensates of dilute atomic gases, superfluid helium and superconductors, the existence of vortices is a consequence of the quantum nature of the system. Quantized vortices of supercurrent are generated by magnetic flux penetrating the material, and play a key role in determining the material properties and the performance of superconductor-based devices. At high temperatures the dynamics of such vortices are essentially classical, while at low temperatures previous experiments have suggested collective quantum dynamics. However, the question of whether vortex tunnelling occurs at low temperatures has been addressed only for large collections of vortices. Here we study the quantum dynamics of an individual vortex in a superconducting Josephson junction. By measuring the statistics of the vortex escape from a controllable pinning potential, we demonstrate the existence of quantized levels of the vortex energy within the trapping potential well and quantum tunnelling of the vortex through the pinning barrier. [ABSTRACT FROM AUTHOR]

The first part of this paper is concerned with the proof of a discrete analog of the Poisson summation formula. In the second part, we describe an elementary proof of a functional equation for the function θ(t), based on the summation formula derived in the paper. [ABSTRACT FROM AUTHOR]

The detailed analysis carried out in this work shows that the Russian budgetary system is extraordinarily cumbersome and inefficient. It has a host of systemic shortcomings that cannot be resolved using macroeconomic policy measures. The principal systemic problem of the Russian budget is the imbalance between spending obligations and the revenue base. The true scale of the spending portion of the budget is significantly higher than the official statistics show—according to estimates, it is about 53 percent of GDp while revenues are only 37 percent of GDP (in 1999). The principal economic policy goal in the near term should be eliminating this gap by pursuing structural reforms. In view of the small possibilities for raising additional revenues, the principal direction of state policy should be reducing expenditures. But such reductions are impossible without profound structural transformations in the budget sphere. These would go beyond the bounds of fiscal policy, and include structural and institutional reforms in the social sphere, defense, and state administration. The revenue side of the budget should also be reformed. This pertains principally to the tax system, which has become one of the main impediments to economic growth. Tax reform should emphasize reduction and even distribution of the tax burden, as well as increased efficiency of tax monitoring and administration. If these structural reforms are implemented, within five to ten years the Russian budget should decline to 40-42 percent of GDP with zero deficits. This roughly corresponds to the lower limits of budgets in the countries of the Organization for Economic Cooperation and Development (OECD). [ABSTRACT FROM AUTHOR]

Evaluates the capability of low temperature scanning laser microscopy for imaging submillimeter waves in cryoelectronic circuits. Spatial distribution of time-averaged field amplitudes; Characterization of cryoelectronic devices; Wave patterns in integrated superconducting received chips.

Reports on high frequency measurements of underdamped Josephson junction arrays consisting of two rows of parallel biased cells. Radio frequency voltage generated on the junctions; Enhancement of the microwave power from the junctions; Output power from two row arrays of different geometries.

Studies spatially resolved measurements of critical current parameters in superconducting filaments by low temperature laser scanning microscopy (LTLSM). Voltage response of different filaments; Comparison of critical currents obtained from standard non-local and local LTSLM measurements; Distribution of critical currents.

Reports on radiation measurements with a double-junction stacked Josephson flux-flow oscillator on-chip coupled to an SIS detector. How impedance matching between the oscillator and the detector was achieved; Measurement of radiation power in the detector.

Magnetic field dependence of current-voltage characteristics of 7-layer stacked Nb/Al-AlO/sub x//Nb long Josephson junctions are investigated experimentally. The magnetic coupling between the junctions is provided by their common superconducting electrodes of the thickness smaller than the London penetration depth. The current-voltage characteristics clearly display collective flux-flow behaviour of Josephson vortices (fluxons) which simultaneously move in up to 5 layers of the stack under the influence of the bias current. The flux-flow behaviour is modulated by a complicated structure of cavity-like resonances which show a broad range of characteristic frequencies. Our observations can be qualitatively explained as the interplay between the Fiske modes and the two-dimensional resonances in these stacks. For the intermediate magnetic field range, we find pronounced resonant modes with large voltage spacing which indicates mutually coherent operating junctions. [ABSTRACT FROM PUBLISHER]

Examines a system of two vertically stacked niobium/Al-AlO[sub x]/Nb long Josephson junctions. Observation of magnetic coupling between junctions; Examination of current-voltage characteristics of the stack displaying resonant steps; Application of stacked long Josephson junctions as local oscillators for millimeter and submillimeter wave circuits.

Spatiotemporal dynamics of the polarisation state of laser radiation performed by lens-axicon combinations were investigated theoretically and numerically in the paraxial regime. We demonstrate that in this case, while the static polarisation state does not change, various features are observed in the temporal dynamics, including spiral trajectories of the field components, transformation of the polarisation state and the "disappearance" of the light field at some time moments of the harmonic period. The results obtained can be useful for understanding the effects of spatiotemporal polarisation transformations of laser radiation, which is crucial in the field of ultrastrong and ultrashort laser-matter interactions. • Lens-axicon combinations provide transformations of laser radiation polarisation state. • Spatiotemporal dynamics of the polarisation state are investigated theoretically and numerically. • The obtained results are useful for understanding effects of ultrashort laser-matter interactions. [ABSTRACT FROM AUTHOR]