Coarse-Grained Picture for Controlling Complex Quantum Systems

We propose a coarse-grained picture to control ``complex'' quantum dynamics, i.e., multi-level-multi-level transition with a random interaction. Assuming that optimally controlled dynamics can be described as a Rabi-like oscillation between an initial and final state, we derive an analytic optimal field as a solution to optimal control theory. For random matrix systems, we numerically confirm that the analytic optimal field steers an initial state to a target state which both contains many eigenstates.Comment: jpsj2.cls, 2 pages, 3 figure files; appear in J. Phys. Soc. Jpn. Vol.73, No.11 (Nov. 15, 2004

Positron Lifetime Spectroscopy of Silicon Nanocontainers for Cancer Theranostic Applications

Biocompatibility and biodegradability of porous silicon (por-Si) nanoparticles (NPs), as well as the fact that they can selectively accumulate in tumor tissues, allow using them as containers for delivery of diagnostic markers or drugs for therapy of cancer tumors. Advantages of por-Si NPs as carriers of drugs are also favorable due to the high surface area and large pore volume. To apply por-Si NPs as nanocontainers it is necessary to have the comprehensive information about their porosity. In our work we use the positron annihilation lifetime (PAL) spectroscopy for porosity investigation. Samples of por-Si were prepared by electrochemical etching of heavily boron doped crystalline Si wafers in a hydrofluoric acid solution. The prepared por-Si films were dried and mechanically milled to obtain powder of NPs, which was pressed into tablets for PAL investigation. Ortho-positronium components of the measured positron lifetime spectra allowed us to evaluate the pore size distribution in por-Si NPs as continuous bimodal one with two peaks near 1 nm and 3 nm. Keywords: positron annihilation lifetime spectroscopy, positronium, porous silicon nanoparticles, nanocontainers, porosimetry, theranostics

Carcinogenicity Screening of Chemicals Using Positron Annihilation Spectroscopy

Chemical carcinogens are the main cause of cancer. Many thousands of new chemicals are synthesized annually in the world, unknown part of them is carcinogens. There are several methods, which are currently used for testing carcinogenicity. The fastest arephysicochemical methods. We suggest the method of fast carcinogen screening using the positron annihilation spectroscopy (PAS). It is based on the fact that the presence of carcinogens, being strong electrophiles, significantly decreases positronium (Ps) formation probability. This quantity can be measured by means of conventional PAS techniques: positron annihilation lifetime spectroscopy (PALS), angular correlation of annihilation radiation (ACAR) or Doppler broadening of annihilation radiation (DBAR). It is also possible to evaluate anti-carcinogenic properties of chemicals using the anti-inhibition effect of Ps formation. Keywords: carcinogen, electrophilicity, positron annihilation spectroscopy, positroniu

Gain switching of an external cavity grating-coupled surface emitting laser with wide tunability

The gain-switched, single frequency operation of an external cavity grating-coupled surface emitting laser with a wavelength tuning range of 100 nm was presented. The light in the grating section was coupled out of the laser at a specific angle to the surface of the device. Analysis showed that within the driving current range, lasing in the device only occurred when the external cavity was properly aligned

Point-by-point inscription of 250-nm-period structure in bulk fused silica by tightly-focused femtosecond UV pulses: experiment and numerical modeling

By conducting point-by-point inscription in a continuously moving slab of a pure fused silica at the optimal depth (170 μm depth below the surface), we have fabricated a 250-nm-period nanostructure with 30 nJ, 300 fs, 1 kHz pulses from frequency-tripled Ti:sapphire laser. This is the smallest value for the inscribed period yet reported, and has been achieved with radical improvement in the quality of the inscribed nanostructures in comparison with previous reports. The performed numerical modeling confirms the obtained experimental results

Widely tunable gain-switched operation of external cavity grating-coupled surface emitting laser

Widely tunable gain switching of a grating-coupled surface-emitting laser (GCSEL) has been demonstrated in a simple external cavity configuration for the first time. Pulse duration in range of 40-100ps and wavelength tuning over 100nm have been achieved. High power, tail-free optical pulses have been observed at 980nm

Estimated Inpatient Hospital Stay in Individual Wards: Guidelines on Radiation Safety after Radioiodine Therapy

Radionuclide therapy safety requirements are regulated by the Russian Radiation Safety Standards (RRSS), which state the maximum allowed radionuclide activity in the body and the equivalent dose rate (EDR) of gamma radiation. Therefore, it is necessary to estimate the time of an inpatient hospital stay in specially designed radionuclide therapy wards. The article presents the findings of individual 131I biokinetics studies in 64 patients admitted to radioiodine therapy of thyrotoxicosis and differentiated thyroid cancer. We developed a method to calculate the time interval to reach the EDR of 20μSv/h and the recommended EDR of 3 and 0.3μSv/h for adults and children, respectively. It is based on the measurement of the 131I excretion constant. Keywords: Radioiodine therapy, Radiation safety, Guidelin

Exceptional orthogonal polynomials and the Darboux transformation

We adapt the notion of the Darboux transformation to the context of polynomial Sturm-Liouville problems. As an application, we characterize the recently described $X_m$ Laguerre polynomials in terms of an isospectral Darboux transformation. We also show that the shape-invariance of these new polynomial families is a direct consequence of the permutability property of the Darboux-Crum transformation.Comment: corrected abstract, added references, minor correction

Exceptional Askey-Wilson type polynomials through Darboux-Crum transformations

An alternative derivation is presented of the infinitely many exceptional Wilson and Askey-Wilson polynomials, which were introduced by the present authors in 2009. Darboux-Crum transformations intertwining the discrete quantum mechanical systems of the original and the exceptional polynomials play an important role. Infinitely many continuous Hahn polynomials are derived in the same manner. The present method provides a simple proof of the shape invariance of these systems as in the corresponding cases of the exceptional Laguerre and Jacobi polynomials.Comment: 24 pages. Comments and references added. To appear in J.Phys.