We propose an implementation of the straight-line fit algorithm to evaluate data obtained as part of measurements of line structures, e.g. a grating line, which allows us to determine, at a conventional threshold value, the coordinates of the edges, the position and the width of its photometric profile as well as the related standard uncertainty contribution. These are derived for the (1 − α)100% confidence intervals with α [0, 1]. The implementation is demonstrated using data obtained by the PTB Nanometer Comparator (Fluegge and Köning 2001 Proc. SPIE 4401 275–83). The investigation revealed that large parts of the uncertainty of the position and the width of the line are due to the choice of the fit interval and the uncertainty of the determination of the minimum and maximum level of the ...

The Physikalisch-Technische Bundesanstalt (PTB) has substantially improved the quality of its local time scale UTC(PTB), which is the national realization of the international time reference Coordinated Universal Time (UTC). It serves as the basis for PTB's time services, for local clock comparisons and for international time comparisons. Since February 2010 UTC(PTB) has been realized using an active hydrogen maser (AHM) steered in frequency via a phase micro-stepper according to an algorithm which combines the frequency comparison data between the AHM and primary and commercial caesium clocks of PTB. Thereby the long-term stability and accuracy of PTB's primary clocks, in particular its fountain clock CSF1, were combined with the short-term frequency stability of the AHM. CSF1 data were used to calculate the steering on all but six days during 15 months. During the time between July 2010 and July 2011, the time difference between UTC(PTB) and UTC was always less than 6 ns and th...

The future mise en pratique for the realization of the kelvin will be founded on the melting temperatures of particular metal–carbon eutectic alloys as thermodynamic temperature references. However, at the moment there is no consensus on what should be taken as the melting temperature. An ideal melting or freezing curve should be a completely flat plateau at a specific temperature. Any departure from the ideal is due to shortcomings in the realization and should be accommodated within the uncertainty budget. However, for the proposed alloy-based fixed points, melting takes place over typically some hundreds of millikelvins. Including the entire melting range within the uncertainties would lead to an unnecessarily pessimistic view of the utility of these as reference standards. Therefore, detailed analysis of the shape of the melting curve is needed to give a value associated with some identifiable aspect of the phase transition. A range of approaches are or could be used; ...

Pure edge 90° misfit dislocations (MDs) are the most effective linear defects that combine the substrate and the film with different lattice parameters. A system consisting of a nonstressed film and a substrate approaches the perfect case in terms of the structural transition from one lattice parameter to the other if imperfections in the form of an ordered network of edge MDs are located exclusively at the interface, while threading dislocations are practically absent. The path to this perfect case goes through studying the possibilities of creating such an ordered network of edge MDs. The mechanism of formation of edge MDs proposed previously by Kvam et al (1990 J. Mater. Res. 5 1900) is discussed. This mechanism involves induced formation of a complementary pair of 60° MDs whose coalescence at the interface creates an edge MD. Some publications are presented, which demonstrate on the basis of experimental data that this mechanism under certain conditions c...

For maximum fibre-coupled power, high power broad area diode lasers must operate with small lateral far field angles at high continuous wave (CW) powers. However, these structures are laterally multi-moded, with low beam quality and wide emission angles. In order to experimentally determine the origin of the low beam quality, spectrally resolved near and far field measurements were performed for a diode laser with 50 µm stripe width. Within the range measured (CW optical output powers to 1.5 W) the laser is shown to operate in just six stable lateral modes, with spatially periodic profiles. Comparisons of the measured profiles with the results of two-dimensional modal simulation demonstrate that current-induced thermal lensing dominates the lateral waveguiding, in spite of the presence of both strong built-in index guiding and gain guiding. No evidence is seen for filamentation. Building on the diagnosis, proposals are presented for improvements to beam quality.

Direct detection thin-film bipolar narrow-gap Hg _{1− x}Cd _x Te semiconductor is considered as a waveguide THz/sub-THz bolometer. The response of such thin layer detectors was calculated and measured in the ν = 0.037–1.54 THz frequency range at T ∼ 70–300 K. Noise equivalent power of such detectors can reach NEP _{300 K} ∼ 4 × 10 ⁻¹⁰ W Hz ^−1/2 and NEP _{100 K} ∼ 10 ⁻¹¹ in the low-frequency part of the sub-THz spectral range.

We present and discuss results for the experimental evaluation of bi-SQUIDs with shunted submicron cross-type Josephson tunnel junctions characterized by low capacitance. Such a technology, meant for SQUID sensors, was developed to enable unshielded operation of the sensors and to avoid unwanted flux trapping. The obtained voltage response swing is as high as 60 µV. The observed differences between the measured and theoretically predicted voltage responses are analyzed and the possible ways to approach a triangular voltage response shape are discussed. An improved design of such bi-SQUIDs with gradiometric topology is suggested to compensate for the influence of the sizable parasitic three-junction loop, which is the main drawback of the implemented bi-SQUID topology.

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Using the chiral quark model, the system is studied by the Gaussian expansion method. Two configurations, i.e. diquark–antidiquark and molecular structures, are employed in the calculation. In the pure diquark–antidiquark or the molecular structure configuration, no bound state is found. However, the energy of the state with I( J ^P) = 0(1 ⁺) is found to be lower than the corresponding threshold after taking into account the mixture of the two configurations. Future experimental research of this state is needed to check the validity of the channel coupling effect of the different color structures and th...

We have observed the blazar Markarian 421 with the TACTIC γ-ray telescope at Mt. Abu, India, from 22 November 2009 to 16 May 2010 for 265 h. Detailed analysis of the data so recorded revealed the presence of a TeV γ-ray signal with a statistical significance of 12.12σ at E _γ ⩾ 1 TeV. We have estimated the time-averaged differential energy spectrum of the source in the energy range 1.0–16.44 TeV. The spectrum fits well with the power-law function of the form (d F/d E = f ₀ E ^−Γ) with f ₀ = (1.39 ± 0.239) × 10 ⁻¹¹ cm ⁻² s ⁻¹ TeV ⁻¹ and Γ = 2.31 ± 0.14.