A HELP system for the user community

Interactive computer guidance systems are discussed. The user interface of such systems and the computer resources required are examined for a large computer centre. The design and development of a Liverpool HELP system is discussed. The Liverpool HELP system, which is written entirely in GEORGE job control language, is shown to be an efficient and inexpensive solution to the provision of an on-line enquiry service.     

Efficiency of modified urea fertilizers for tropical irrigated rice

An objective of the International Network on Soil Fertility and Fertilizer Evaluation for Rice (INSFFER) network is to field evaluate deep-point placement (urea supergranules) and slow-release (sulfur coated urea) N fertilizers in irrigated rice. These N sources were compared for performance with split application of prilled urea at 19 sites in Asia in wet season 1981.SCU or USG differed significantly in response curves from prilled urea at 12 of the 17 sites where N response was observed. Over these 17 sites, 22–25% less N as SCU or 29–31% less N as USG provided the same yield increment as the comparatively higher level of N as prilled urea.High profit N rates were derived for 5 sites. The optimal N levels for SCU or USG were less than for prilled urea. However, in one case for both test materials prilled urea was more profitable than SCU or USG. The marginal rates of return of using SCU or USG as opposed to OPU were calculated for the 11 sites where the response functions of the test materials differed significantly from prilled urea. In other than 2 sites for SCU the MRR exceeded 2.0 for 29 and 58 kg N ha^–1, indicating the general profitability of these materials when compared to prilled urea.     

Precipitation and dissolution of solids attending flow through porous media

A model is developed that calculates the chemical equilibrium that exists between a flowing electrolyte solution and mineral assemblages. The development computes the mineral and aqueous compositions as a function of time and position in a one-dimensional porous medium. The model considers the dissolution of solids as well as their precipitation. The application of the model to various problems has revealed that characteristic aqueous and solid phase concentration waves develop and propagate through the system in a chromatographic manner. Example calculations are presented that illustrate the widespread applicability of the model. Specifically, a calculation is presented that reproduces the genetic mineralization features that are found in sandstone-type uranium deposits.     

Microbeam RBS on flat panel displays

We have demonstrated the utility of microbeam-Rutherford BackScattering (μ-RBS) in spatially resolved studies of operational plasma effects on the interior surfaces of plasma flat panel displays manufactured by Photonics Imaging. The experiments were performed at the Sandia Nuclear microprobe using a 2.8 MeV He beam with an average beam spot size of less than 8 μm. The interior surface of the top panes of the flat panels is composed of approximately 800 nm of MgO on top of a 2000 nm thick PbO layer. μ-RBS of sample panels operated under varying conditions measured changes in the surface MgO film thickness due to plasma erosion and redeposition as accurately as ± 1.5 nm. The high accuracy in the MgO thickness measurement was achieved by inferring the MgO thickness from the shift of the Pb front edge in the RBS spectrum. An estimate for the thickness accuracy as a function of the acquired statistics is presented. The surface of the flat panels' bottom panes is also comprised of MgO on top of PbO. However, troughs 100 μm wide by 10 μm deep were partially filled with phosphor and cover the entire width of the surface. This leaves only 100 μm long sections of MgO within the trough exposed. Using μ-RBS, we were able to analyze the surface composition of these regions.     

Rupture recurrence after surgical repair of postinfarction ventricular septal rupture. Influence of early thrombolysis

OBJECTIVES: The aim of this study was to identify factors causing rupture recurrence after surgical repair of postinfarction ventricular septal rupture and to evaluate the indication for reoperation. PATIENTS: Recurrence of rupture was analysed in 25 out of a series of 109 patients who underwent surgical repair for postinfarction ventricular septal rupture between 1980 and 1992 in our institution. RESULTS: The mean interval between initial operation and recurrence was 3.6 days with a median of 2 days. Multivariate logistic regression analysis identified early thrombolysis after infarction (P = 0.0085) as a risk factor for recurrence of the rupture. Rupture recurrence occurred more in the anterior then in the posterior infarction site, although non-significant. Reoperation was indicated in 15 patients, in 13 for postrecurrent cardiac failure. The main determinant of cardiac failure was a large postrecurrent shunt (P = 0.05). The mean interval between initial operation and reoperation was 136 days with a median of 101 days. In 6 patients a combined apical ventricular septal rupture recurrence and anterior ventricular aneurysm was found, in 9 patients the recurrent rupture was proximally located, without concomitant aneurysm formation. Of 15 patients who were reoperated, one died in hospital and three after the in-hospital period. Of 10 patients treated conservatively, one died in hospital and two after the in-hospital period. One residual ventricular septal rupture closed spontaneously. CONCLUSIONS: Rupture recurrence is mainly determined by early thrombolysis. Postrecurrent cardiac failure, as the main indication for reoperation, is dependent on postrecurrent shunt size.     

Sequence analysis of the CCG polymorphic region adjacent to the CAG triplet repeat of the HD gene in normal and HD chromosomes

The CAG expansion responsible for Huntington's disease (HD) is followed by an adjacent polymorphic CCG repeat region which may interfere with a PCR based diagnosis. We have sequenced this region in 52 unrelated HD patients, from both normal and HD chromosomes. Fifty percent of the normal alleles were (CCG)7(CCT)2, 48% (CCG)10(CCT)2, and 2% (CCG)7(CCT)3. In contrast (CCG)7(CCT)2 was found in 85% of the HD alleles which represents significant linkage disequilibrium with the HD mutation.     

Direct evidence for the role of haem doming as the primary event in the cooperative transition of haemoglobin

The study of cooperative ligand binding among the four subunits of haemoglobin has played a central role in the understanding of allosteric transitions in a large number of enzymes. Haem iron out-of-plane motion has been suggested to be the trigger for the cooperative transition of haemoglobin. To function as a trigger in a dynamic sense, haem-iron doming must be the first conformational change to occur following ligand dissociation. Here we present the first direct demonstration that haem-iron doming occurs on the same time scale as the breaking of the iron-ligand bond, thus establishing haem-iron doming as the primary event which lead to the R-->T transition in haemoglobin.