Multistable generation of monochromatic radiation in solid-state lasers

It is shown that a solid-state laser with unpumped sections of action medium which act as a saturable absorber, may operate in a stable, single-mode cw lasing regime. The establishment of lasing in a particular mode under steady-state conditions depends on the initial conditions of transient evolution. Pis’ma Zh. Tekh. Fiz. 24, 89–92 (February 26, 1998)     

Damage production in GaAs during MeV ion implantation

The influence of the nuclear and electronic energy loss on the damage production in GaAs has been studied by Se⁺ ion implantation at T_I = 293 K with energies ranging from 2 MeV up to 20 MeV. The ion dose was varied between 5 × 10¹² /cm² and 1 × 10¹⁵ /cm². The damage production was investigated using RBS in channeling regime. Temperature and energy dependent backscattering measurements and TEM investigations were performed to study the kind of defects in more detail. The resulting defect profiles are compared with the depth distribution of the nuclear and electronic energy loss which were simulated by TRIM 87. The results show that the remaining defect concentration strongly decreases with increasing implantation energy even if the same energy density is deposited into nuclear processes. We suppose, that the electronic energy loss increases the defect transformation and annealing during implantation at T_I = 293 K. The defects in the samples implanted with energies greater than 5 MeV are characterized as point defects, point defect clusters and small dislocation loops; the kind of defects are the same over the whole implantation depth and the existence of amorphous zones can be widely excluded.     

Transient thermo-reflectance measurements of the thermal conductivity and interface resistance of metallized natural and isotopically-pure silicon

The transient thermoreflectance method has been used to measure the thermal conductivity of natural silicon and isotopically-pure silicon-28 layers that are epitaxially grown on natural silicon substrates. The measurements were performed at room temperature for both a low level (10¹⁶) and a higher level (2×10¹⁹) of Boron doping of the epitaxial layers. The results indicate a gain of approximately 55% in the thermal conductivity of Si²⁸ as compared to that of natural Si, at both low and higher levels of doping, and a loss of approximately 19% for both types of silicon due to the higher level of doping.     

Cytotoxic activity of platelets and peripheral blood mononuclear cells from oncology patients and healthy donors

Testicular germ cell tumour is said to be a model for curable neoplasm. However, the prognosis of primary extragonadal germ cell tumour does not appear to be as promising. Though similar in histology, the biology of primary extragonadal germ cell tumour is different as exemplified by the patients in this review. Eight patients with primary mediastinal germ cell tumours were treated with intensive cisplatin-based chemotherapy. All, except one, had non-seminomatous components. The poor prognosis of mediastinal germ cell tumour is due to a combination of poor treatment results with the cisplatin-based regimen and the development of non-germ cell and haematological malignancies.     

Interaction of tetravalent uranium with the chloride-fluoride melt NaCl−KCl−NaF

The method of measuring the oxidation-reduction potential of U(HI)/ U (IV) was used to investigate the interaction of uranium tetrachloride with a chloride-fluoride melt. The measurements were performed in a molten equimolar mixture of sodium and potassium chlorides, containing 3% by weight U and 8.0–18.5% by weight NaF, within the interval 973–1123°K. It was established that U⁺⁴ forms the fluoride complex UF^?2 in a melt of the investigated composition. An expression was found for the temperature dependence of the instability constant of this complex in a NaCl–KC1–NaF melt:

$$\overline {\log } K = 0.95 - \frac{{16 200}}{T} \pm 0.25.$$     

Physical modeling of phenomena of the interaction of hydraulic structures with water in the presence of an air curtain

Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 10, pp. 18–24, October, 1992.