ALBERT

Notes: Abstract The northern Pacific asteroid Asterias amurensis (Lütken) has been recently introduced to Tasmania and is now well-established in east and southeast Tasmania. This sea star is conspicuous throughout the Derwent River estuary and is particularly abundant in the Hobart port area. Reproduction of two populations of A. amurensis at Sullivans Cove and at Sandy Bay was investigated from August 1993 to October 1994 by gonadal histology and measurement of the gonad index (GI). An intense period of vitellogenic and spermatogenic growth started in April, with the breeding condition reached by June. In 1994, peak GI was recorded at Sullivans Cove in July and at Sandy Bay in August. Although these data indicated that the Sullivans Cove population spawned before the Sandy Bay population, histological examination revealed that major spawning activity occurred in both populations from July onwards. In the early part of the breeding season, gametogenesis proceeded in parallel with spawning, with released gametes being replaced by continual gametogenesis. Maintenance of a higher GI during the early part of the breeding season at Sandy Bay was due to prolonged gametogenic replacement at this site. Spawning continued to October 1994, resulting in a sharp decline in the GI. The cyclic expansion and regression of the genital haemal sinus coincident with germinal proliferation and growth, respectively, support the contention that haemal fluid provides nutrients for gametogenesis. In Tasmania, A. amurensis experiences temperature and photoperiod regimes similar to those experienced by endemic populations of this species in the north Pacific. Comparison of reproduction of A. amurensis in Japan and Tasmania at similar latitudes shows that gametogenesis of the northern and southern populations is 6 mo out of phase. This phase shift provides evidence for photoperiodic regulation of gametogenesis in A. amurensis. The similar trend in sea-temperature regimes associated with the stages of gametogenesis in northern and southern populations suggests that temperature also plays a modulatory role. Based on the periodicity of reproduction and the ontogeny of A. amurensis, the planktotrophic larvae of this species would be expected to be in the plankton for several months from the end of winter through summer. Considering the highly fecund, dispersive life-history of A. amurensis, the southeast Tasmanian populations have considerable potential to serve as a seed source for establishment of new populations of this asteroid elsewhere in Tasmania and in mainland Australia.

Notes: Abstract Biotinidase deficiency is an autosomal recessively inherited disorder in the recycling of the vitamin biotin. The most common mutation that causes profound biotinidase deficiency in symptomatic individuals is a deletion/insertion (G98:d7i3) that occurs in exon B of the biotinidase gene. We now report the second most common mutation, a C-to-T substitution (position 1612) in a CpG dinucleotide in exon D of the biotinidase gene. This mutation results in the substitution of a cysteine for arginine538 (designated R538C) and was found in 10 of 30 symptomatic children with profound biotinidase deficiency, 5 of whom also have the G98:d7i3 mutation. This mutation was not found in DNA samples from 32 individuals with normal biotinidase activity, but was found in one individual with enzyme activity in the heterozygous range. This mutation was not detected in 371 randomly selected, normal individuals using allele-specific oligonucleotide hybridization analysis. Aberrant biotinidase protein was not detectable in extracts of fibroblasts from a child who is homozygous for the R538C mutation, but was present in less than normal concentration in identical extracts treated with β-mercaptoethanol. Because there is no detectable biotinidase protein in sera of children who are homozygous for the R538C mutation and in combination with the deletion/insertion mutation, the R538C mutation likely results in inappropriate intra- or intermolecular disulfide bond formation, more rapid degradation of the aberrant enzyme, and failure to secrete the residual aberrant enzyme from the cells into blood.

Notes: Shear induced changes in the demixing conditions are discussed for the copolymer blends of the present type in terms of a distortion of quasichemical equilibria established in the stagnant systems between the two different kinds of polymer segments. Calculations were performed in an attempt to rationalize experimental results obtained with blends exhibiting upper critical solution temperatures. The proposed model accounts for the experience that the first observable effect of shear consists of an enlargement of the two-phase regime (a behavior which differs fundamentally from that of homopolymer blends or homopolymer solutions) and yields the correct order of magnitude for the effects. The influences of copolymer composition, number of segments of the components, and temperature dependence of the Flory-Huggins interaction parameter are discussed in detail. Furthermore, it is demonstrated how the present considerations relate to an earlier approach based on the energy a system can store while it flows. © 1999 American Institute of Physics.

Notes: A method is presented that allows the calculation of phase diagrams (spinodal, binodal, and tie lines) of quaternary mixtures on the basis of the Gibbs energy of mixing ΔG. No derivatives of ΔG with respect to the composition variables are required. This method is particularly useful in cases where the composition dependence of ΔG is very complex, and no analytical representation of ΔG can be found. Phase diagrams have been calculated on the basis of the Flory–Huggins theory for mixtures of four polymers. Blends that phase separate because of very favorable interactions (negative interaction parameters) were of particular interest. In this case miscibility gaps can be located inside the tetrahedron composed of the Gibbs phase triangles of the four completely miscible ternary subsystems. For symmetrical mixtures of K components (identical chain lengths and interaction parameters) equations are presented that allow the calculation of K-phase and (K−1)-phase regions for any value of K. © 1995 American Institute of Physics.

Notes: The present calculations were performed on the basis of the Sanchez-Lacombe-Balasz lattice fluid theory. The two system specific parameters cursive-epsilon12* and δcursive-epsilon* required for that purpose have been obtained from the spinodal temperatures measured (SANS) for mixtures of poly(vinyl methyl ether) (PVME) and deuterated polystyrenes (d-PS) by Schwahn and coworkers. The experimental data reported for atmospheric pressure and six representatives of the present system are well described theoretically, where cursive-epsilon12* does not depend on molar mass and δcursive-epsilon* decreases only slightly as the chain length of d-PS is raised. The measured pressure influences on the spinodal conditions correspond to an approximately linear reduction of δcursive-epsilon* with increasing P; this observation should reflect the volume changes associated with the formation of specific interactions. According to the present calculations the critical composition shifts markedly towards pure PVME as P is raised. Since experimental data are commonly expressed in terms of the Flory-Huggins theory, the current results were also translated into Flory-Huggins interaction parameters and evaluated with respect to the contributions of enthalpy and of entropy. The agreement between experimental information and that calculated from the Sanchez-Lacombe-Balasz lattice fluid theory is reasonable. © 1997 American Institute of Physics.

Notes: Using an effective (coarse-grained) thermodynamic potential describing the excess free energy of mixing of a polymer solution and fitting its parameters to measured critical point data, we obtain the "hump'' ε(τ) of this potential in the two-phase region (τ being the reduced distance from the critical temperature T of unmixing). For 30 different systems (varying the degree of polymerization r as well as choosing different polymer–solvent pairs) it is shown that the data are reasonably well represented by a power law, ε(τ)=εˆττζ. While mean field theory implies ζ=5/2 and scaling theory ζ=3ν+β≈2.22 (using Ising model exponents ν≈0.63,β≈0.325), the "effective'' exponent extracted from the data mostly falls in between these limits (ζeff≈2.4). Since the interfacial tension satisfies a similar power law, σ(τ)=σˆττμ (with μ=3/2 in mean field theory or μ=2ν≈1.26 in scaling theory), we also consider a relation between interfacial tension and free energy hump, σ(ε)=σˆεεcursive-phi. While mean-field theory implies cursive-phi=3/5 and scaling theory cursive-phi=2/(3+β/ν)≈0.57, the empirical exponent lies in the range 0.5(approximately-less-than)cursive-phieff(approximately-less-than)0.6. We present estimates of molecular weight dependencies of critical amplitude prefactors εˆτ,σˆτ,σˆε and of related quantities for many different systems. We also discuss whether the critical amplitude combination (εˆτ/Bˆτ)2/3/σˆ, where Bˆτ describes the coexistence curve {φcoex(2)−φcoex(1)=Bˆττβ} is universal. Contrary to some theoretical expectations, our data imply that this combination is not universal, and hence it cannot be used to predict interfacial tensions from equation of state data. © 1995 American Institute of Physics.

Notes: The pulsed magnetic field (PuMa)-electron cyclotron resonance (ECR) ion source uses a pulsed coil to improve the peak current by opening the magnetic bottle along the beam axis. After demonstration of the principle of the pulsed magnetic extraction, the ion source was tested with different gases. We received promising results from helium to krypton. The influence of the current in the pulsed coil on the analyzed ion current was measured. With increased current levels within the pulsed coil not only the pulse height of the PuMa pulse, but the pulse length can also be controlled. By using the pulsed coil the maximum of the charge state distribution can be shifted to higher charge states. © 1996 American Institute of Physics.

Notes: The microwave plasma cathodes (MPC) dedicated to high-current ion sources are characterized by long lifetime with reactive gases and a compact structure. An Ishikawa-type MPC developed at GSI Darmstadt coupled with the CHORDIS ion source is presented. The electron current of the MPC is extracted from a dense plasma generated under electron-cyclotron-resonance condition. The axial magnetic field is produced by permanent magnets and ferromagnetic components. The 2.45 GHz microwave power (some tens of watts) is introduced into the plasma chamber via a coaxial line ended with a helical antenna. Experiments with argon and oxygen gas are presented and discussed. © 1996 American Institute of Physics.

Notes: The sinter density of small superconducting BSCCO samples (Bi2Sr2Can−1CunOy; n=1, 2, or 3; y about 7) was determined by hydrostatic weighing using a special technique to correct the mass data for penetration of immersion liquid. A discontinuity in the reevaporation curve permits one to distinguish between liquid, penetrated into the sample, and that adhering to the surface of the specimen. This allows one to calibrate by wiping away of excess liquid without fluid extraction out of sample pores. © 1995 American Institute of Physics.