Real-time and two-reference-beam hologram interferometry: effects of emulsion shrinkage

When transmission holograms are recorded on photographic materials, any change in the thickness of the photographic emulsion due to processing can produce a change in the spacing of the carrier fringes. We show that the resulting change in the angle at which the image is reconstructed when the hologram is illuminated with the original reference beam can give rise to significant errors in real-time and two-reference-beam hologram interferometry.     

Superachromatic lens combinations

Achromatic objectives are constructed by combining two or more lenses with properly chosen powers made of materials with different dispersions. We present a new approach that simplifies the design of multilens achromatic combinations as well as the choice of materials for them and show how this method can be applied to the design of a four-lens superachromatic combination.     

A new spectral collocation method for solving Bratu-type equations using Genocchi polynomials

Journal of Mathematical Chemistry - In this paper, we have introduced a new Genocchi polynomial approximation method for solving Bratu-type equations arising in Engineering. With the help of...     

Influence of Variant Electrolyte in Electrochemical Micromachining of Micro Holes in SMA Using Taguchi Optimization

Russian Journal of Electrochemistry - Electrochemical micromachining (ECMM) is one of the commercially successful modern machining processes used in various manufacturing industries. Nitinol, a...     

Crystal structure of solid C70

Detailed analysis of the room temperature X-ray powder diffraction data of pure solid C₇₀ is reported. C₇₀ prepared by slow evaporation from toluene solution adopts an hcp structure (space groupP6₃/mmc) witha=10·53(1) A andc=17·24(1) A. C₇₀ sublimed on to Si wafer adopts an fcc structure witha=14·89(1) A. The occurrence of both the hcp and fcc phases is rationalized in terms of cohesive energy calculations. Theoretical calculations of the diffraction pattern for the hcp structure, taking into account (a) orientational disorder amongst the molecules (b) presence of stacking faults and (c) a fraction of the sample to be amorphous/microcrystalline is seen to provide very good agreement with the experimental diffraction pattern.     

Broad-band optical isolator

We describe an optical isolator which can be constructed with standard optical components and used with a laser to minimize optical feedback over a wide range of wavelengths.     

Double grating interferometer with variable lateral shear

A modified Ronchi interferometer using two identical gratings is described. This instrument is very suitable for the measurement of small, zonal aberrations, since the shear can be changed continuously by rotating one grating with respect to the other, while the direction and magnitude of the tilt between the sheared wavefronts can be varied by adjusting the distances of the two gratings from the centre of the gaussian sphere.     

Direct evidence for the decomposition of YBa2Cu3O7−x into orthorhombic and tetragonal phases at 200°C

The variations of room temperature resistivity (ρ ₃₀₀), powder a.c. susceptibility (χ′) and x-ray diffraction (XRD) line profiles of (013), (103) and (110); (003), (010) and (100) reflections in the step scanning mode were investigated on single phase samples of Y₁Ba₂Cu₃O_7−x (YBCO), as a function of ageing at 200°C up to 860 h. The average off-stoichiometryx=0.22 remained constant throughout the experiment.ρ ₃₀₀ showed a monotonic increase while the superconducting transition curves showed increasing sharpening with ageing time. XRD of the reflections investigated developed satellite structures or additional intensities at 2θ values different from those of main reflections. The results are consistent with the prediction and earlier observation of the decomposition of the off-stoichiometric YBCO into oxygen ordered orthorhombic and vacancy ordered tetragonal phases.     

Synthesis of 4-(4-iodophenyl)piperazine and the 1-carboxamidino derivative

The previously unreported 4-(4-iodophenyl)piperazine ( 2 ) was synthesized in a 70% yield and characterized. The reaction of 2 with S-methylthiouronium sulfate gave the corresponding carboxamidino derivative 4 in a 61% yield. The tlc properties of 4 were identical with those of the radioiodinated material that had been prepared and evaluated as a potential myocardial imaging radiopharmaceutical.     

Double grating interferometers II. Application to collimated beams

The application of a shearing interferometer consisting of two identical gratings to measurements of the aberrations of collimated beams is described. The theory of the system is derived, and it is shown how the shear as well as the tilt between the sheared wavefronts can be varied.