Influence of hydrogen on the thermoelectric voltage signal in a Pt/WO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/6<Emphasis Type="Italic">H</Emphasis>-SiC/Ni/Pt layered structure

The possibility of detecting H₂ by registering the thermal electromotive force signal, which arises between the surfaces of 6H-SiC plates with a thickness of 400 μm, is established. The working surface of the plates is modified by deposition of a WO _x film and catalytic Pt. An ohmic contact (Ni/Pt) is created on the rear surface of the plate, and this surface is maintained at a stabilized temperature of 350°C. The temperature gradient through the plate thickness arises due to the cooling of the working surface with the air medium. The delivery of H₂ into this medium up to a concentration of 2% gives rise to a 15-fold increase in the electric signal, which considerably exceeds the Pt/WO _x /SiC/Ni/Pt system’s response registered in the usual way by measuring the current–voltage dependence. In this case, an additional power source for the registration of the thermal electromotive force is not required.     

Platelet-derived growth factor-specific regulation of the JE promoter in rat aortic smooth muscle cells

JE is a member of the family of "immediate early" genes induced by growth factors and cytokines. JE encodes a low molecular weight secretory glycoprotein analogous to the human monocyte chemoattractant protein, MCP-1. JE and MCP-1 proteins are thought to play an important role in inflammation and in the recruitment of monocyte/macrophages to the vessel wall during the development of atherosclerosis. We have previously reported that the induction of JE in rat aortic smooth muscle cells (SMC) was specific to platelet-derived growth factor (PDGF) and was not seen with other growth agonists. Using a luciferase reporter system and transient transfection assays of rat aortic SMC, we now report the identification of a region in the proximal rat JE promoter that is responsive to PDGF but not to other growth factors (angiotensin II and alpha-thrombin) or cytokines (interleukin 1-beta and tumor necrosis factor-alpha). The full response to PDGF (approximately 6-fold) requires the cooperative activity of two potentially novel cis-acting elements, at positions -146 to -128 and -84 to -59. While each element produces a different pattern in electrophoretic mobility shift assays, they appear to bind the same PDGF-responsive species. Further analysis of these regions should provide important insights into PDGF-specific responses in vascular SMC.     

The three-dimensional neutron kinetics coupled with thermal-hydraulics in RBMK accident analysis

The RBMK core is a complex ensemble of high-pressure high-temperature tubes, graphite bricks, low-pressure low-temperature control rod tubes, graphite interstitial gas passages. An about 7 MPa boiling light water crosses the around 19 m long vertical tubes (7 m active length). The lattice consisting of graphite columns and hydraulic channels is bounded by the reactor cavity whose resistant elements are the metal cylindrical tank and thick circular top and bottom plates with proper holes for the passage of tubes.Related to a typical water cooled reactor, the peculiarities of the RBMK core can be summarized as follows: (a) large dimensions – the overall core volume is by far the largest for a nuclear power plant (NPP) producing electricity; (b) use of separate moderator and coolant constituted by graphite and light boiling water, respectively – the boiling water mostly absorbs neutrons in this environment leading to the (small) positive void reactivity coefficient; (c) presence of water channels very close to each other containing coolant at different temperatures (543–557 K and 350 K for fuel channels (FC) and control and protection system (CPS) channels, respectively); (d) presence of core-wide radial, core-wide axial and local temperature gradients in the graphite bricks with temperature values in the range 330–650 K with the high-temperature values justified by the neutron moderation and gamma-heating processes.Owing to the above peculiarities, the development and the use of a three-dimensional neutron kinetics code (3D NK) coupled with a one-dimensional thermal-hydraulic (TH) code is essential in RBMK safety analyses.Two approaches have been used within the present context, i.e. use of coupled 3D NK-TH codes to support the accident analysis in the RBMK as discussed in the first of the companion papers in this journal volume: application of Korsar-Bars making use of the Unk code to derive λ-matrices needed for Bars and of Relap5/3D-Nestle making use of the Helios code to derive the macroscopic cross-sections.Bounding transient analyses of accident scenarios including control rod withdrawal, various Loss of Coolant Accident (LOCA) and discharge of the control rod circuit, have been completed. In all of the analysed cases, starting from nominal operating conditions, modest fission power time gradients have been found, i.e. characterized by time derivative values for local and global power changes substantially smaller than current values accepted in safety analyses of light water reactors.     

Assembly and analysis of conical models for the HIV-1 core

The genome of the human immunodeficiency virus (HIV) is packaged within an unusual conical core particle located at the center of the infectious virion. The core is composed of a complex of the NC (nucleocapsid) protein and genomic RNA, surrounded by a shell of the CA (capsid) protein. A method was developed for assembling cones in vitro using pure recombinant HIV-1 CA-NC fusion proteins and RNA templates. These synthetic cores are capped at both ends and appear similar in size and morphology to authentic viral cores. It is proposed that both viral and synthetic cores are organized on conical hexagonal lattices, which by Euler's theorem requires quantization of their cone angles. Electron microscopic analyses revealed that the cone angles of synthetic cores were indeed quantized into the five allowed angles. The viral core and most synthetic cones exhibited cone angles of approximately 19 degrees (the narrowest of the allowed angles). These observations suggest that the core of HIV is organized on the principles of a fullerene cone, in analogy to structures recently observed for elemental carbon.