Structure Investigations of Islands with Atomic-Scale Boron-Carbon Bilayers in Heavily Boron-Doped Diamond Single Crystal: Origin of Stepwise Tensile Stress.

The detailed studies of the surface structure of synthetic boron-doped diamond single crystals using both conventional X-ray and synchrotron nano- and microbeam diffraction, as well as atomic force microscopy and micro-Raman spectroscopy, were carried out to clarify the recently discovered features in them. The arbitrary shaped islands towering above the (111) diamond surface are formed at the final stage of the crystal growth. Their lateral dimensions are from several to tens of microns and their height is from 0.5 to 3 µm. The highly nonequilibrium conditions of crystal growth enhance the boron solubility and, therefore, lead to an increase of the boron concentrations in the islands on the surface up to 1022 cm-3, eventually generating significant stresses in them. The stress in the islands is found to be the volumetric tensile stress. This conclusion is based on the stepwise shift of the diamond Raman peak toward lower frequencies from 1328 to 1300 cm-1 in various islands and on the observation of the shift of three low-intensity reflections at 2-theta Bragg angles of 41.468°, 41.940° and 42.413° in the X-ray diffractogram to the left relative to the (111) diamond reflection at 2theta = 43.93°. We believe that the origin of the stepwise tensile stress is a discrete change in the distances between boron-carbon layers with the step of 6.18 Å. This supposition explains also the stepwise (step of 5 cm-1) behavior of the diamond Raman peak shift. Two approaches based on the combined application of Raman scattering and X-ray diffraction data allowed determination of the values of stresses both in lateral and normal directions. The maximum tensile stress in the direction normal to the surface reaches 63.6 GPa, close to the fracture limit of diamond, equal to 90 GPa along the [111] crystallographic direction. The presented experimental results unambiguously confirm our previously proposed structural model of the boron-doped diamond containing two-dimensional boron-carbon nanosheets and bilayers.

Formation of Boron-Carbon Nanosheets and Bilayers in Boron-Doped Diamond: Origin of Metallicity and Superconductivity.

The insufficient data on a structure of the boron-doped diamond (BDD) has frustrated efforts to fully understand the fascinating electronic properties of this material and how they evolve with doping. We have employed X-ray diffraction and Raman scattering for detailed study of the large-sized BDD single crystals. We demonstrate a formation of boron-carbon (B-C) nanosheets and bilayers in BDD with increasing boron concentration. An incorporation of two boron atoms in the diamond unit cell plays a key role for the B-C nanosheets and bilayer formation. Evidence for these B-C bilayers which are parallel to {111} planes is provided by the observation of high-order, super-lattice reflections in X-ray diffraction and Laue patterns. B-C nanosheets and bilayers minimize the strain energy and affect the electronic structure of BDD. A new shallow acceptor level associated with B-C nanosheets at ~37 meV and the spin-orbit splitting of the valence band of ~6 meV are observed in electronic Raman scattering. We identified that the superconducting transitions occur in the (111) BDD surfaces only. We believe that the origin of Mott and superconducting transitions is associated with the two-dimensional (2D) misfit layer structure of BDD. A model for the BDD crystal structure, based on X-ray and Raman data, is proposed and confirmed by density functional theoretical calculation.

[Change in the density of surface lymphocyte receptors and in the level of serum immunoglobulins in chronic lympholeukosis]. / Izmenenie plotnosti retseptorov na poverkhnosti limfotsitov i urovnia syvorotochnykh immunoglobulinov pri khronicheskom limfoleikoze.

Using the complex of methods for recognition of surface lymphocyte receptors the authors examined 42 patients with chronic lymphatic leukemia and 30 healthy individuals. The reduced density of receptors on lymphocyte surface or their total absence is characteristic of the whole group of patients with chronic lymphatic leukemia. This atypism of leukemia lymphocytes is augmented in greater rate of neoplastic cells growth. Total synthesis of serum immunoglobulins in chronic lymphatic leukemia is found to be lowered, the fall being more sharp in increased amount of lymphocytes in peripheral blood.

[The role of prevention in decreasing endocrine pathology]. / K voprosu o roli profilaktiki v snizhenii éndokrinnoi patologii.

Time course of changes in the incidence of thyroid diseases and their association with other noncontagious chronic diseases (NCCD) have been evaluated among therapeutic patients hospitalized at Research Center for Clinical and Experimental Medicine of Siberian Division of Russian Academy of Medical Sciences in 1983-1995. The incidence of thyroid diseases was low in 1983, when prevention of iodine-deficiency diseases was a state program. In 1989, when iodine deficiency prevention was reduced, the incidence of cases with enlarged gland and its dysfunction has drastically increased. In 1995, when the system of population protection from endemic goiter virtually ceased to function, the incidence of thyroid diseases increased, including such serious diseases as diffuse toxic goiter, nodular goiter, primary hypothyrosis, and autoimmune thyroiditis; the number of patients in whom thyroid diseases were concomitant with other NCCD increased. These results demonstrate the principal significance of the preventive trend in public health.

[Advantages in immunofluorescence of dichlortriazinylaminofluorescein conjugates isolated by single-step gel filtration]. / Preimushchestva v immunofliuorestsentsii dikhlortriazinilaminofliuorestseinovykh kon"iugatov, vydeliaemykh odnostupenchatoi gel'-filtratsiei

The author describes a simple method obtaining dichlortriazinylaminofluoresceine (DCTAF) conjugates to human immunoglobulins and separation of their optimally labeled fractions. The single-stage method of the conjugate release from the nonbound flurorchrome and of a simultaneous separation of the optimally labeled fractions was carried out on Sephadex G-25 at pH 5.6--6.6 and at low ionic power of the eluate. Proteins overloaded with the dye are sorbed on gel according to their isoelectrical points.

[Catalytic and immunochemical properties of ferritin conjugates with horseradish peroxidase]. / Kataliticheskie i immunokhimicheskie svoistva kon''iugata ferritina s peroksidazoi iz khrena.

The human spleen ferritin--horseradish peroxidase conjugate (HRP--Fer) was synthesized by periodate oxidation of the enzyme carbohydrate fragment. The protein fraction containing 1-2 peroxidase molecules and characterized by kinetic homogeneity was obtained in the peroxidatic ortho-dianisidine (o-DA) oxidation reaction. Gel diffusion precipitation of HRP--Fer with peroxidases and ferritin antibodies was carried out. The precipitation confirms the retention by peroxidase and ferritin of their antigenic properties. The kinetics of peroxidatic oxidation of o-DA by the HRP--Fer conjugate was studied within the temperature interval of 15-37 degrees C. The value of catalytic constant for this reaction exceeds that for native peroxidase 1.75-fold. A kinetic analysis of thermal inactivation of peroxidase and its conjugate was performed within the temperature range of 40-65 degrees C. The effective rate constants of inactivation obtained from the first order equation are higher for HRP--Fer than for the native enzyme. The effect of pH on the rates of inactivation of HRP--Fer and the non-modified enzyme was studied at 50 degrees C. The enzyme and its conjugate were shown to stabilize in acid media. The HRP--Fer conjugate can be used as an effective tool in immunoenzymatic assays of ferritin.

[Glycemia as a risk factor of reduced tolerance of hypoxic hypoxia in flight personnel]. / Glikemiia kak faktor riska ponizhennoi perenosimosti gipoksicheskoi gipoksii u letnogo sostava.

The glycemic level was measured in 61 people exposed to hypoxic hypoxia. Three major types of glycemic responses were identified: type I--no change (15.79%); type II--hypoglycemia (49.12%), and type III--hyperglycemia (35.09%). The subjects with a low resistance to hypoxic hypoxia typically showed a low glycemic level (57.5 +/- 2.5 mg%. P < 0.05). It is suggested that three types of glycemic responses to hypoxia reflect three major pathways of biochemical adaptation of the body. It is recommended to study hormonal changes in people with hyperglycemic responses to hypoxia. This will help determine hormonal levels responsible for hyperglycemia and, consequently, develop methods of early detection of susceptibility to cardiovascular diseases and diabetes mellitus. This approach may contribute to medical expertise and rehabilitation of the flying personnel.

[Systemic and cerebral hemodynamic status of flight personnel under moderate hypoxia]. / Sostoianie obshchei i tserebral'noi gemodinamiki u lits letnogo sostava v usloviiakh umerennoi gipoksii.

For the purposes of medical expertise the state of systemic and cerebral hemodynamics has been investigated in 66 pilots with autonomic-vascular instability and in 36 healthy subjects exposed to moderate hypoxia (in an altitude chamber). The pilots have shown noticeable tachycardia or systolic hypertension as well as certain changes in cardiac output and stroke volume. These alterations have been accompanied by rheoencephalographic changes of two types one of which can be regarded as an adverse response of cerebral circulation to hypoxia. It is concluded that the study of systemic and cerebral circulation in hypoxia yields an important diagnostic information that allows better expertise estimates.

Polymerization of nitrogen in sodium azide.

The high-pressure behavior of nitrogen in NaN(3) was studied to 160 GPa at 120-3300 K using Raman spectroscopy, electrical conductivity, laser heating, and shear deformation methods. Nitrogen in sodium azide is in a molecularlike form; azide ions N(3-) are straight chains of three atoms linked with covalent bonds and weakly interact with each other. By application of high pressures we strongly increased interaction between ions. We found that at pressures above 19 GPa a new phase appeared, indicating a strong coupling between the azide ions. Another transformation occurs at about 50 GPa, accompanied by the appearance of new Raman peaks and a darkening of the sample. With increasing pressure, the sample becomes completely opaque above 120 GPa, and the azide molecular vibron disappears, evidencing completion of the transformation to a nonmolecular nitrogen state with amorphouslike structure which crystallizes after laser heating up to 3300 K. Laser heating and the application of shear stress accelerates the transformation and causes the transformations to occur at lower pressures. These changes can be interpreted in terms of a transformation of the azide ions to larger nitrogen clusters and then polymeric nitrogen net. The polymeric forms can be preserved on decompression in the diamond anvil cell but transform back to the starting azide and other new phases under ambient conditions.

[New information technologies in the management of emergency health services]. / Novye informatsionnye tekhnologii v upravlenii sluzhboi skoroi meditsinskoi pomoshchi.

Novel information computer system introduced at the first aid station of Novosibirsk has improved effectiveness of ambulance transport and emergency teams; quickened the process of reporting information to the head of the station and higher medical institutions as well as responding to requests; facilitated control over continuous education of the staff and planning of relevant educational programs.