First Results of the Implementation of the Doppler Backscattering Diagnostic for the Investigation of the Transition to H-Mode in the Spherical Tokamak Globus-M2.

This paper presents the first results of a study of the LH transition on the new spherical Globus-M2 tokamak using the Doppler backscattering (DBS) diagnostic. New data characterizing the H-mode of discharges with higher values of the plasma parameters, such as magnetic field Bt up to 0.9 T and plasma current Ip up to 450 kA, were collected and analyzed. An upgraded neutral beam injection (NBI) system was used to initiate the LH transition. DBS allows the measurement of the poloidal rotation velocity and the turbulence amplitude of the plasma. The multi-frequency DBS system installed on Globus-M2 can simultaneously collect data in different areas spanning from the separatrix to the plasma core. This allowed for the radial profiles of the rotation velocity and electric field to be calculated before and after the LH transition. In addition, the values and temporal evolution of the velocity shear were obtained. The associated turbulence suppression after the transition to the H-mode was investigated using DBS.

Endovenous laser coagulation: asymmetrical heat transfer and coagulation (modeling in blood plasma).

The objective of this study was to describe the dynamics of blood plasma heating and coagulation processes carried out by continuous laser radiation with wavelengths 1.55 and 1.94 µm through bare-tip fibers and fibers with radial output (radial fibers) used for endovenous laser coagulation (EVLC). The study was performed in previously thawed frozen donor blood plasma using high-speed shooting of the heating process through the shadow optical method. It has been shown that in the case of highly water-absorbed laser radiations, convection, explosive, and small-bubble boiling play a major role in the process of heat transfer and coagulation. It has been shown that in the case of radiation with wavelength λ = 1.94 µm, effective heat transfer begins at significantly lower levels of power compared to radiations with λ = 1.55 µm. It has been established that heat transfer is sharply asymmetrical and is directed mainly upwards and forwards (bare-tip fiber) or upwards (radial fibers). For a wavelength of 1.94 µm, the effect of self-cleaning of the fiber surface from coagulated plasma fragments was found. Except for short-term acts of explosive boiling, the heat transfer is asymmetrical and directed mainly upwards. This effect should lead to uneven heating and thermal damage to the vein wall with the maximum at its upper part. For EVLC, the use of radiation with a wavelength of 1.94 µm is more efficient and safer.

Endovenous laser coagulation: asymmetrical heat transfer (modeling in water).

The objective of this study was to describe the dynamics of water heating carried out by continuous laser radiation with wavelengths 1.47, 1.55, and 1.94 µm with different types of fibers used for endovenous laser coagulation. The study was conducted in water using high-speed surveying of the heating process through the shadow optical method. It has been shown that in the case of highly water-absorbed laser radiations, convection and boiling play a major role in the process of heat transfer. It has been shown that in the case of radiation with λ = 1.94 µm that is heavily absorbed by water, effective heat transfer begins at significantly lower levels of power compared to the weaker-absorbed radiations with λ = 1.47 and 1.55 µm. Mathematical models based only on thermal conductivity inadequately describe the process of real heat transfer during endovenous laser coagulation. It has been established that heat transfer is sharply asymmetrical and is directed mainly up-and-forward (bare-tip fiber) or upward ("radial" and "two-ring" fibers). Heat transfer for laser light with wavelength 1.94 µm is most effective than for 1.47 and 1.55 µm.

Differential interference contrast tomography.

We present a new approach to optical tomography of phase objects that is referred to as differential interference contrast tomography (DICT). The main feature of DICT is that the result of tomographic reconstruction is a 3D DIC image. This image is described by partial derivative of 3D refractive index distribution in one direction. The DICT setup consists of a lateral shearing phase-shifting interference microscope with low-coherent LED illumination. To create projections of the sample at various illumination angles, an angular scanning beam was used. 3D DIC tomograms of a white blood cell are presented. The comparison between the reconstructed DIC tomogram slices and the conventional DIC images of the same sample at the same depths are also represented.

Advanced method of phase shift measurement from variances of interferogram differences.

A new approach to the problem of measuring the phase shift from variances of interferogram differences based on Fourier domain analysis is proposed. It is shown that the use of true variance of the interferogram differences and spatial apodization of interferograms increases the accuracy of the phase shift of the measurement. Numerical simulations and experiments are presented.

Ex vivo laser thermoplasty of whole costal cartilages.

BACKGROUND AND OBJECTIVE: To examine the possibilities of laser thermoplasty of whole costal cartilages for correction the human congenital chest wall deformities. STUDY DESIGN/MATERIALS AND METHODS: Ex vivo the samples of porcine costal cartilages were heated with lasers of differing wavelengths, including a 0.97-µm diode laser, a 1.56-µm erbium-doped quartz fiber laser, and a 1.68-µm fiber Raman laser. The dynamics of the temperature fields and the degradation of collagen in the laser-affected regions of samples were determined by using, respectively, thermometry, trypsin treatment, and light microscopy. Ex vivo the whole mechanically deformed costal cartilages of pigs were treated by laser radiation with wavelength 1.68-µm. The changes of cartilage shape were recorded at certain intervals over a 24-hour period by photographing them in a fixed position with a digital camera. RESULTS: Treatment of costal cartilage samples from 5 to 11 mm in thickness by laser radiation with 0.97, 1.56, and 1.68 µm wavelengths showed that the 1.68-µm radiation could produce the necessary nonuniform bulk heating of the exposed sample. The altered shape of costal cartilage proved to remain stable after treatment when the laser irradiation settings used provided for the heating of a broad region within the tissue to temperatures about 80°C. CONCLUSION: This study demonstrates the possibilities of laser thermoplasty of whole costal cartilages for treatment of human congenital chest wall deformities. The development of novel approaches based on laser cartilage engineering techniques will enable to treat the human congenital chest wall deformities.