ALBERT

Notes: Abstract A domain-adaptive technique which maps a time-dependent, curvilinear geometry into a unit square is used to determine the steady state mass absorption rate and the collapse of annular liquid jets. A method of lines is used to solve the one-dimensional fluid dynamics equations written in weak conservation-law form, and upwind differences are employed to evaluate the axial convective fluxes. The unknown, time-dependent, axial location of the downstream boundary is determined from the solution of an ordinary differential equation which is nonlinearly coupled to the fluid dynamics and gas concentration equations. The equation for the gas concentration in the annular liquid jet is written in strong conservation-law form and solved by means of a method of lines at high Peclet numbers and a line Gauss-Seidel method at low Peclet numbers. The effects of the number of grid points along and across the annular jet, time step, and discretization of the radial convective fluxes on both the steady state mass absorption rate and the jet's collapse rate have been analyzed on staggered and non-staggered grids. The steady state mass absorption rate and the collapse of annular liquid jets are determined as a function of the Froude, Peclet and Weber numbers, annular jet's thickness-to-radius ratio at the nozzle exit, initial pressure difference across the annular jet, nozzle exit angle, temperature of the gas enclosed by the annular jet, pressure of the gas surrounding the jet, solubilities at the inner and outer interfaces of the annular jet, and gas concentration at the nozzle exit. It is shown that the steady state mass absorption rate is proportional to the inverse square root of the Peclet number except for low values of this parameter, and that the possible mathematical incompatibilities in the concentration field at the nozzle exit exert a great influence on the steady state mass absorption rate and on the jet collapse. It is also shown that the steady state mass absorption rate increases as the Weber number, nozzle exit angle, gas concentration at the nozzle exit, and temperature of the gases enclosed by the annular liquid jet are increased, but it decreases as the Froude and Peclet numbers, and annular liquid jet's thickness-to-radius ratio at the nozzle exit are increased. It is also shown that the annular liquid jet's collapse rate increases as the Weber number, nozzle exit angle, temperature of the gases enclosed by the annular liquid jet, and pressure of the gases which surround the jet are increased, but decreases as the Froude and Peclet numbers, and annular liquid jet's thickness-toradius ratio at the nozzle exit are increased. It is also shown that both the ratio of the initial pressure of the gas enclosed by the jet to the pressure of the gas surrounding the jet and the ratio of solubilities at the annular liquid jet's inner and outer interfaces play an important role on both the steady state mass absorption rate and the jet collapse. If the product of these ratios is greater or less than one, both the pressure and the mass of the gas enclosed by the annular liquid jet decrease or increase, respectively, with time. It is also shown that the numerical results obtained with the conservative, domain-adaptive method of lines technique presented in this paper are in excellent agreement with those of a domain-adaptive, iterative, non-conservative, block-bidiagonal, finite difference method which uncouples the solution of the fluid dynamics equations from that of the convergence length.

Notes: A comprehensive picture of the tokamak stability limits against ideal magnetohydrodynamic (MHD) pressure-gradient-driven modes is put forward. The approach is based on scaling arguments for large q, and affords a first principle understanding of the Troyon limit once the normalized ratio βaB/I is modified by an extra q0 factor. The effects related to a possible access to the second stability region are clarified.

Notes: We discuss the fluctuation characteristics expected from MHD modes including ballooning modes and show how they can be studied using measurements of ECE. A novel technique, ECE correlation radiometry, which enables the location and spatial structure of long wavelength (L(approximately-greater-than)0.1×a) MHD modes to be determined, is described. Measurements on JET with a 44-channel ECE heterodyne radiometer are presented and show the existence of high-frequency (high n number) MHD modes under high poloidal beta, pellet-enhanced performance (PEP) plasma conditions. Similar measurements are planned for PBX-M and the measurement system is described.

Notes: Shallow, 1–40 nm deep steps were ion beam milled at 60° angle of incidence to the normal of the MgO substrate in order to form Josephson junctions. Microbridges were patterned across the step boundary in films of YBa2Cu3O7−δ. They displayed critical current densities and critical current-normal resistance products that, on the whole, decreased with increasing step height, leveling off at about 5 nm. Transmission electron microscopy showed the presence of 45° [001]-tilt regions in the films close to the steps. Interferometers (dc-SQUIDs) showed magnetic field response at temperatures above 77 K and a noise level of about 1.5×10−8 Φ02/Hz at 10 Hz and 4.2 K.

Notes: Stimulation of transcription from the Pseudomonas TOL plasmid xylS gene promoter (Ps) and the upperpathway operon promoter (Pu) is dependent on the positive regulator protein XylR activated by an effector molecule such as 3-cholorotoluene, and on RpoN, an RNA polymerase sigma factor. Mutational analysis of the Ps and Pu promoters showed that upstream activator sequences located between -110 and -218bp upstream of the main transcription initiation point are required for regulated expression from these promoters. A search for homologous nucleotide sequences in the -110to -218bp region in Pu and Ps revealed conserved sequences that may act as putative recognition sequences for the XylR protein. Ps and Pu exhibit another well-conserved region at around 50 bp, which is homologous to corresponding sites in other RpoN-dependent promoters and may constitute a binding site for integration host factor (IHF).

Notes: Abstract A {2 21} twin lamella in undoped LEC InP was studied by means of a diluted sirtl mixture applied with light (DSL) photoetching and microRaman spectroscopy. This study revealed that there was defect segregation at the twin boundary. This boundary-defect-depletion area would result in an enhanced photocarrier lifetime and a stress relaxation that extends a few micrometres away the boundary. From these results, it appears that the formation of this twin was strongly influenced by stoichiometry fluctuations during growth; these fluctuations were revealed by both selective photoetching and by microRaman scanning spectroscopy.

Notes: Abstract Gene regulation studies in pseudomonad bacteria are mainly restricted to Pseudomonas aeruginosa and Pseudomonas putida. Constitutive promoters exhibit DNA sequences similar to the σ 70-dependent constitutive promoters of Escherichia coli. The TOL meta-cleavage pathway operon promoter and the nah operon promoters are the best characterized σ 70-dependent promoters, which exhibit-10 regions rich in As and Ts and non-conserved-35 regions. The DNA binding motif recognized by the respective positive regulators lies between-40 and-80. Another set of positively controlled promoters exhibit upstream activator sequences located between-100 and-500. Transcription stimulation from some of these promoters also involves σ 54 and/or IHF protein. In this class of promoters, DNA binding is required to establish open complexes. Promoters for the utilization of histidine (hut) are under negative control by the HutC protein. hut promoters exhibit-10/-35 consensus regions and an overlapping operator sequence between-15 and-50. Repression of hut promoters seems to be achieved through steric hindrance of RNA polymerase. Another set of promoters are controlled by catabolite repression, which seems to be cyclic-AMP independent.