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Notes: The work function of tetrahedral amorphous carbon (ta-C) has been measured by Kelvin probe to lie in the range 4–5 eV, irrespective of its sp3 content or nitrogen addition. This implies that the surface barrier to emission is dominant and that emission changes caused by sp3 bonding or nitrogen addition are not directly due to changes in work function. Hydrogen, oxygen, and argon plasma treatments are all found to increase the emission of a-C, but hydrogen and argon treatments are found to reduce the work function while oxygen treatment increases it. Detailed studies of the surface with varying plasma treatment conditions suggest that the changes in emission arise mainly from changes in the surface microstructure, such as the formation of sp2 regions within the sp3 bulk. The need for local field enhancement mechanisms to account for emission over the sizeable barrier is emphasized, which may arise from local chemical nonhomogeneity, or formation of nanometer-size sp2 clusters embedded in an sp3 matrix. © 2000 American Institute of Physics.

Notes: Conventionally, the simulation of thin films has been carried out using an HCP structure to represent its physical structure. Such an idealized structure has been shown to overestimate the effect of interparticle coupling by using an homogeneous exchange coupling scheme. A more realistic approach to represent physical structure has been undertaken by generating a system of grains which lie on a radially isotropic structure and have a nonuniform volume distribution. Interaction effects can be shown by computing δI curves formed through the comparison of the remanence curves using the Wohlfarth relation. To generate an isothermal remanence curve (IRM), a realistic ac erased state is necessary which has been carried out by using a simulated annealing technique. A comparison has been made to determine the effect of physical structure on the bulk properties by computing hysteresis loops, remanence curves, and δI curves. To reduce statistical error these have been averaged over four different sets of easy axes. The loops indicate that an irregular physical structure leads to an increase in the coercivity and decrease in the squareness. The dc-demagnetization curves show an increase in remanent coercivity; this can be attributed to the random physical structure decreasing the size of magnetically correlated regions within the microstructure. The effect of the physical microstructure on the δI curves will be discussed in full in the paper. © 1996 American Institute of Physics.

Notes: The supercurrent in a Nb–In0.53Ga0.47As/In0.77Ga0.23As/InP weak link structure is controlled by means of a current injected into the two-dimensional electron gas. For small injection currents the critical current to control current ratio is as large as 20. The measured features can be qualitively explained in terms of a modification of the Andreev level occupation by the injected carriers. © 1998 American Institute of Physics.

Notes: To understand the mechanism of electron field emission from diamond-like carbon, tetrahedral amorphous carbon (ta-C) films were subjected to Ar, H2, and O2 plasma treatments to change their surface condition and were deposited on substrates of different work function. The threshold fields and current densities for undoped ta-C are found to be significantly improved by the plasma treatments, largely due to an increase in emission site density, while little dependence was found on work function of substrate. This suggests that the main barrier to emission from ta-C is at the front surface. © 1999 American Institute of Physics.

Notes: Superconducting Nb–In0.53Ga0.47As/In0.77Ga0.23As/InP–Nb contacts with an electrode separation of 450 nm were fabricated. Due to the high mobility of the two-dimensional electron gas, the current transport can be described within the clean limit regime. At 0.3 K a critical current of 3.8 μA was obtained for 6 μm wide contacts leading to a characteristic voltage of 190 μV. The decrease of the critical current with increasing temperature can be explained by a theory developed by A. Chrestin, T. Matsuyama, and U. Merkt [Phys. Rev. B 49, 498 (1994)], which takes δ-shaped barriers at the superconductor/semiconductor interfaces into account. © 1997 American Institute of Physics.

Notes: Field emission has been measured from a series of tetrahedrally bonded amorphous carbon (ta-C) films produced by the filtered cathodic vacuum arc. The threshold field and current densities achievable have been studied as a function of their sp3 content and of nitrogen incorporation. Typical undoped ta-C films are found to have a threshold field of 10–20 V/μm, decreasing with increasing sp3 content, and optimally nitrogen doped films exhibit threshold fields as low as 3–5 V/μm. © 1997 American Institute of Physics.

Notes: Optimized sputtered YBa2Cu3O7 (YBCO) thin films on CeO2-buffered sapphire substrates are patterned into square lattices of submicrometer holes (antidots) with diameters of 250–450 nm and lattice parameters of d=500–1000 nm without deterioration of superconducting properties. In the mixed state, matching effects between the Abrikosov vortex lattice and the artificial antidot lattice are observed. These effects are in the form of peaks or cusps in the critical current density recorded as a function of magnetic induction at integers n and specific rationals k/l of the matching field Bm=(Φ0/d2). The experimental results are discussed in the context of existing theories. The existence of multiquanta vortices confined by the holes in YBCO films are considered. © 1997 American Institute of Physics.

Notes: A comprehensive study of the stress release and structural changes caused by postdeposition thermal annealing of tetrahedral amorphous carbon (ta-C) on Si has been carried out. Complete stress relief occurs at 600–700 °C and is accompanied by minimal structural modifications, as indicated by electron energy loss spectroscopy, Raman spectroscopy, and optical gap measurements. Further annealing in vacuum converts sp3 sites to sp2 with a drastic change occurring after 1100 °C. The field emitting behavior is substantially retained up to the complete stress relief, confirming that ta-C is a robust emitting material. © 1999 American Institute of Physics.

Notes: Eight experiments aimed at improving methods for the village-based farming of giant clams were conducted in the Solomon Islands. The experiments focused on either improving the fitness of seed clams delivered to village farmers, assessing whether differential growth rates of seed clams in nursery tanks persisted during grow-out at farms, or testing the effects of alterations to the design of grow-out cages on the growth and survival of clams. We found that Tridacna squamosa (Lamarck) ‘seed’ transferred from land-based nursery tanks to a floating ocean nursery (FON) for ≈ 3 months at the end of the nursery phase were significantly larger than seed reared only in land-based nursery tanks. Similarly, T. maxima (Röding) placed in a FON for 2–5 months generally grew at a significantly greater rate than tank-reared ‘seed’. However, the use of FONs did not improve survival. There were no consistent differences in the growth and survival of fast- and slow-growing seed of T. derasa (Röding) at village sites when slow-growing seed were retained in the nursery until reaching a larger size. The survival of T. maxima was enhanced significantly by placing an insert of smaller mesh (a ‘settlement ring’) in grow-out cages for the first 2 months after delivery of seed to farmers. The settlement ring retained clams in cages until they found a suitable place to attach their byssal threads. Attempts to remove the sediment which impedes the attachment of T. maxima to the base of grow-out cages by perforating the substrate did not improve survival: the perforated substrate resulted in poor attachment of clams and harboured predators (Cymatium spp.). The survival of T. crocea (Lamarck) was not improved by ‘softening’ the concrete base of grow-out cages to simulate dead coral rock and to encourage the clams to burrow in the substrate. The survival of T. crocea in grow-out cages was enhanced significantly by enclosing the cages in fine mesh after the delivery of the seed clams to prevent predation and disturbance by juvenile wrasse, Thalassoma spp. The experiments indicate that the critical stage for village farming of giant clams is during the initial weeks following distribution of seed. Further research is needed to improve the survival of T. crocea and T. maxima during this phase.

Notes: Inequalities in health care provision: the relationship between contemporary policy and contemporary practice in maternity services in England Aim. The project Addressing Inequalities in Health: new directions in midwifery education and practice (Hart et al. 2001) was commissioned by the English National Board for Nursing, Midwifery and Health Visiting (ENB). Here, we draw on those research findings to consider current midwifery policy and practice in England. Background. Little guidance on providing equality of care exists for midwives. The Code of Conduct [United Kingdom Central Council for Nursing, Midwifery and Health Visiting (UKCC) 1992] makes no specific requirement for midwives to address issues of inequalities of health in their practice. Recent policy documents emphasize the need to work towards reducing inequalities and to target practice to `disadvantaged clients' without giving guidelines on how to identify and care for target groups. Methods. In-depth studies of midwifery education and service provision were conducted in three very different parts of England. Three months of fieldwork were undertaken at each site, comprising a series of interviews with midwifery educators, managers, students, midwives and service users. Focus groups were also held and observation of classroom sessions and midwifery practice undertaken. Findings. A lack of clear and specific strategies concerning inequalities in health was evident at managerial level. Patchy knowledge of current policy was also evident amongst practising midwives. Specific projects with disadvantaged clients usually resulted from a particular midwife's personal interest or evident local need. All midwives emphasized the importance of `equality of care'. How this was operationalized varied, and `individualized' or `woman-centred' care was assumed to encompass the concept. In the few examples where care was systematically targeted in accordance with policy directives, the midwife's public health role was increased. Conclusion. In the absence of a co-ordinated strategic vision driven by managers, practitioners find difficulty in prioritizing care and targeting resources to disadvantaged clients in line with policy directives. Tensions between policy and practice in the care of `disadvantaged' women clearly exist. Successful implementation of policy at practice level needs: commitment from managers; clarity of purpose in documentation; and provision of specific targets for practitioners. However, the latter should remain flexible enough for the delivery of care to be appropriate and sensitive to individual needs.