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Interference of light has numerous metrological applications because the optical path difference (OPD) can be varied at will between the interfering waves in the interferometers. We show how one can desirably change the optical path difference in diffraction. This leads to many novel and interesting metrological applications including high-precision measurements of displacement, phase change, refractive index profile, temperature gradient, diffusion coefficient, and coherence parameters, to name only a few. The subject fundamentally differs from interferometry in the sense that in the latter the measurement criterion is the change in intensity or fringe location, while in the former the criterion is the change in the visibility of fringes with an already known intensity profile. The visibility can vary from zero to one as the OPD changes by a half-wave. Therefore, measurements with the accuracy of a few nanometers are quite feasible. Also, the possibility of changing the OPD in diffraction allows us to use Fresnel diffraction in Fourier spectrometry, to enhance or suppress diffracted fields, and to build phase singularities that have many novel and useful applications.

Background: Most addicts relapse in the first year of treatment especially in the first 3 -6 months, which is the most vulnerable period.

Background: The use of metaphors rather than direct suggestions of treatment can help to weaken defense mechanisms against any functional changes and so cause an increase in the effectiveness of therapeutic interventions. Objectives: This research was conducted with the aim of determining the effectiveness of individual metaphor therapy (IMT) in reducing the irrational beliefs and cognitive restructuring of drug addicts undergoing buprenorphine treatment. Patients and Methods: Using a randomized controlled trial (RCT), 100 drug addicts who were referred to MMT/BMT centers in the city of Kermanshah, Iran, from July to September 2014 were selected through single-stage cluster sampling. After excluding 56 patients from the study due to their failure to meet the inclusion criteria, 44 people (37 at the end) were randomly enrolled into the experimental (n = 19) or control groups (n = 18). The SCID-I and the Jones' Irrational Beliefs tests were used as a means of measurement. Ten sessions of IMT (one session per week) were used as the intervention for the experimental group. The controls received routine cognitive restructuring. Data analysis was conducted using a multivariate analysis of covariance (MANCOVA). Results: After adjusting for age and gender, the findings of the study revealed that IMT was significantly effective in reducing the irrational beliefs of approval seeking (P = 0.02), high self-expectation (P = 0.01), frustration reactivity (P = 0.03), anxious over concern (P = 0.02), and perfectionism (P = 0.006). Conclusions: Since IMT can repeatedly neutralize patients' defenses without aggravating their anxiety, and as the therapy can help patients via the development of a new awareness or reformatting the patients' condition, it is recommended that this kind of therapy be used more widely in cognitive restructuring among drug addicts.

In this work, we offer a novel and flexible approach of spectral switches which can be handled more simply by controlling the phase of the diffracted light field of a completely spatially coherent incident beam with spectral profile from a one-dimensional phase step. This scheme has the benefit of easy implementation by simply varying the height of a one-dimensional phase step which causes spectral switches to occur when the step height reaches certain critical values without modulating any properties of the light source. To illustrate this effect, an explicit and analytical expression at an observation point corresponding to the step edge is obtained and some numerical examples are given and examined experimentally. Finally, based on the obtained results, it is shown that this method with the capability of very short response time can be easily applied to information encoding and transmission.

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