Strain control of a bandwidth-driven spin reorientation in Ca3Ru2O7

The layered-ruthenate family of materials possess an intricate interplay of structural, electronic and magnetic degrees of freedom that yields a plethora of delicately balanced ground states. This is exemplified by Ca3Ru2O7, which hosts a coupled transition in which the lattice parameters jump, the Fermi surface partially gaps and the spins undergo a 90∘ in-plane reorientation. Here, we show how the transition is driven by a lattice strain that tunes the electronic bandwidth. We apply uniaxial stress to single crystals of Ca3Ru2O7, using neutron and resonant x-ray scattering to simultaneously probe the structural and magnetic responses. These measurements demonstrate that the transition can be driven by externally induced strain, stimulating the development of a theoretical model in which an internal strain is generated self-consistently to lower the electronic energy. We understand the strain to act by modifying tilts and rotations of the RuO6 octahedra, which directly influences the nearest-neighbour hopping. Our results offer a blueprint for uncovering the driving force behind coupled phase transitions, as well as a route to controlling them.

Phase transitions in the classical simulability of open quantum systems

We introduce a Langevin unravelling of the density matrix evolution of an open quantum system over matrix product states, which we term the time-dependent variational principle-Langevin equation. This allows the study of entanglement dynamics as a function of both temperature and coupling to the environment. As the strength of coupling to and temperature of the environment is increased, we find a transition where the entanglement of the individual trajectories saturates, permitting a classical simulation of the system for all times. This is the Hamiltonian open system counterpart of the saturation in entanglement found in random circuits with projective or weak measurements. If a system is open, there is a limit to the advantage in simulating its behaviour on a quantum computer, even when that evolution harbours important quantum effects. Moreover, if a quantum simulator is in this phase, it cannot simulate with quantum advantage.

Simulating groundstate and dynamical quantum phase transitions on a superconducting quantum computer

The phenomena of quantum criticality underlie many novel collective phenomena found in condensed matter systems. They present a challenge for classical and quantum simulation, in part because of diverging correlation lengths and consequently strong finite-size effects. Tensor network techniques that work directly in the thermodynamic limit can negotiate some of these difficulties. Here, we optimise a translationally invariant, sequential quantum circuit on a superconducting quantum device to simulate the groundstate of the quantum Ising model through its quantum critical point. We further demonstrate how the dynamical quantum critical point found in quenches of this model across its quantum critical point can be simulated. Our approach avoids finite-size scaling effects by using sequential quantum circuits inspired by infinite matrix product states. We provide efficient circuits and a variety of error mitigation strategies to implement, optimise and time-evolve these states.

Strongly correlated condensed matter systems are among those for which quantum simulation should be able to give an advantage. Here, the authors use a translationally invariant tensor network technique to simulate a quantum critical system on a superconducting quantum processor.

838Premature Cardiac Conduction Disease in families, potential role for Implantable Loop Recorder in screening? A Case Series

OnBehalf

Cardiac Risk in the Young (CRY) Ireland

Background

  Cardiac conduction disease (CCD) is a potentially fatal entity. The spectrum ranges from benign clinical course to potentially precipitating sudden cardiac death. Permanent pacemaker (PPM) may benefit affected individuals but the genetic basis of CCD may be underestimated. No prior study has investigated the utility of screening relatives of victims of Sudden Arrhythmic Death Syndrome (SADS) with implantable loop recorders (ILR). 

Methods

 We describe 7 families referred to our inherited cardiac conditions service with a family history of SADS, in whom we identified premature CCD. ILR was utilized in screening the majority of families. 

Results

 Of 63 individuals screened, 31 (49%) had ILR insertion with 7 (11%) requiring PPM implant. 2/31 had normal baseline tests, and were identified post ILR implant. Other CCD not yet meeting clinical significance was detected in 10/31 (32%) individuals. These findings (documented 11 to 330 days post implant) included pauses of 3-5.8 seconds (n = 7), nocturnal bradycardia < 34 bpm (n = 2) and non-sustained polymorphic ventricular tachycardia. Of families undergoing mutation analysis, conventional genetic panels have been negative to date.

Conclusions

 Inherited premature CCD with variable penetrance may be an under-recognized cause of SADS.  To date 12/31 (39%) of individuals with ILR have findings suggesting inherited CCD. As inheritance pattern suggests autosomal dominant transmission, longer follow up may identify more affected individuals. Clinicians involved in SADS family evaluations should consider adding ILR implantation to routine assessment to improve diagnostic yield. We suggest a larger prospective study of consecutive families whose initial investigations following a SADS death have not identified a cause.

Summary of Findings Screening Abnormality Family 1 Family 2 Family 3 Family 4 Family 5 Family 6 Family 7 Bradycardia Yes Yes Yes Yes Yes Yes Yes PR >200 Yes No No No No No No <90% PTHR EST No No No No No No No Arrhythmia on EST Yes No No No No Yes No Pauses > 3s Holter/Telemetry Yes No Yes No Yes No Yes High grade AV block Holter Yes Yes No No No No No ILR: significant to date Yes Yes No No No No - ILR: findings to monitor Yes No Yes Yes No Yes - Provocation Testing No Negative No No No No No Genetics Negative Negative Awaited Awaited Awaited Awaited Negative PTHR predicted target heart rate, EST: exercise stress test

The Lyapunov spectra of quantum thermalisation

Thermalisation in closed quantum systems occurs through a process of dephasing due to parts of the system outside of the window of observation, gradually revealing the underlying thermal nature of eigenstates. In contrast, closed classical systems thermalize due to dynamical chaos. We demonstrate a deep link between these processes. Projecting quantum dynamics onto variational states using the time-dependent variational principle, results in classical chaotic Hamiltonian dynamics. We study an infinite spin chain in two ways-using the matrix product state ansatz for the wavefunction and for the thermofield purification of the density matrix-and extract the full Lyapunov spectrum of the resulting dynamics. We show that the entanglement growth rate is related to the Kolmogorov-Sinai entropy of dynamics projected onto states with appropriate entanglement, extending previous results about initial entanglement growth to all times. The Lyapunov spectra for thermofield descriptions of thermalizing systems show a remarkable semi-circular distribution.

Fluctuation-driven magnetic hard-axis ordering in metallic ferromagnets

We demonstrate that the interplay between soft electronic particle-hole fluctuations and magnetic anisotropies can drive ferromagnetic moments to point along a magnetic hard axis. As a proof of concept, we show this behavior explicitly for a generic two-band model with local Coulomb and Hund's interactions and a spin-orbit-induced easy plane anisotropy. The phase diagram is calculated within the fermionic quantum order-by-disorder approach, which is based on a self-consistent free-energy expansion around a magnetically ordered state with unspecified orientation. Quantum fluctuations render the transition of the easy-plane ferromagnet first order below a tricritical point. At even lower temperatures, directionally dependent transverse fluctuations dominate the magnetic anisotropy, and the moments flip to lie along the magnetic hard axis. We discuss our findings in the context of recent experiments that show this unusual ordering along the magnetic hard direction.

Global assessment of the status of coral reef herbivorous fishes: evidence for fishing effects

On coral reefs, herbivorous fishes consume benthic primary producers and regulate competition between fleshy algae and reef-building corals. Many of these species are also important fishery targets, yet little is known about their global status. Using a large-scale synthesis of peer-reviewed and unpublished data, we examine variability in abundance and biomass of herbivorous reef fishes and explore evidence for fishing impacts globally and within regions. We show that biomass is more than twice as high in locations not accessible to fisheries relative to fisheries-accessible locations. Although there are large biogeographic differences in total biomass, the effects of fishing are consistent in nearly all regions. We also show that exposure to fishing alters the structure of the herbivore community by disproportionately reducing biomass of large-bodied functional groups (scraper/excavators, browsers, grazer/detritivores), while increasing biomass and abundance of territorial algal-farming damselfishes (Pomacentridae). The browser functional group that consumes macroalgae and can help to prevent coral-macroalgal phase shifts appears to be most susceptible to fishing. This fishing down the herbivore guild probably alters the effectiveness of these fishes in regulating algal abundance on reefs. Finally, data from remote and unfished locations provide important baselines for setting management and conservation targets for this important group of fishes.

Hawking radiation and nonequilibrium quantum critical current noise

The dynamical scaling of quantum critical systems in thermal equilibrium may be inherited in the driven steady state, leading to universal out-of-equilibrium behavior. This attractive notion has been demonstrated in just a few cases. We demonstrate how holography-a mapping between the quantum critical system and a gravity dual-provides an illuminating perspective and new results. Nontrivial out-of-equilibrium universality is particularly apparent in current noise, which is dual to Hawking radiation in the gravitational system. We calculate this in a two-dimensional system driven by a strong in-plane electric field and deduce a universal scaling function interpolating between previously established equilibrium and far-from-equilibrium current noise. Since this applies at all fields, out-of-equilibrium experiments no longer require very high fields for comparison with theory.

Inhomogeneous phase formation on the border of itinerant ferromagnetism

A variety of analytical techniques suggest that quantum fluctuations lead to a fundamental instability of the Fermi liquid that drives ferromagnetic transitions first order at low temperatures. We present both analytical and numerical evidence that, driven by the same quantum fluctuations, this first order transition is preempted by the formation of an inhomogeneous magnetic phase. This occurs in a manner that is closely analogous to the formation of the inhomogeneous superconducting Fulde-Ferrel-Larkin-Ovchinnikov state. We derive these results from a field-theoretical approach supplemented with numerical quantum Monte Carlo simulations.

Inhomogeneous magnetic phases: a Fulde-Ferrell-Larkin-Ovchinnikov-like phase in Sr3Ru2O7

The phase diagram of Sr3Ru2O7 contains a metamagnetic transition that bifurcates to enclose an anomalous phase with intriguing properties--a large resistivity with anisotropy that breaks the crystal-lattice symmetry. We propose that this is a magnetic analogue of the spatially inhomogeneous superconducting Fulde-Ferrel-Larkin-Ovchinnikov state. We show-through a Ginzburg-Landau expansion where the magnetization transverse to the applied field can become spatially inhomogeneous-that a Stoner model with electronic band dispersion can reproduce this phase diagram and transport behavior.

Magnetothermoelectric response at a superfluid-Mott-insulator transition

We investigate the finite temperature magnetothermoelectric response in the vicinity of a superfluid-Mott-insulator quantum phase transition. We focus on the particle-hole symmetric transitions of the Bose-Hubbard model, and combine Lorentz invariance arguments with quantum Boltzmann calculations. By means of an epsilon expansion, we find that a nonvanishing thermoelectric tensor and a finite thermal transport coefficient are supported in this quantum critical regime. We comment on the singular Nernst effect in this problem.

Current noise in the vicinity of the 2D superconductor-insulator quantum critical point

Systems near to quantum critical points show universal scaling in response to external probes. We consider whether this scaling is reflected in their out-of-equilibrium fluctuations. We study current noise in the metallic state at the z=1 quantum critical point between a superconductor and an insulator in two dimensions. Using a Boltzmann-Langevin approach within a 1/N expansion, we show that the current noise obeys a universal scaling form S_{j}=TPhi[T/T_{eff}(E)], with T_{eff} proportional, variantsqrt[E]. This treatment recovers Johnson noise in thermal equilibrium and S_{j} proportional, variantsqrt[E] at strong electric fields. The latter differs significantly from both the shot noise in conventional metals (diffusive Fermi liquids) and the free carrier result, due to strong correlations between the critical bosonic excitations. Current-noise measurements could therefore help clarify the physics of the destruction of superconductivity in thin film superconductors.

Nonlinear quantum critical transport and the Schwinger mechanism for a superfluid-mott-insulator transition of bosons

Scaling arguments imply that quantum-critical points exhibit universal nonlinear responses to external probes. We investigate the origins of such nonlinearities in transport, which is especially problematic since the system is necessarily driven far from equilibrium. We argue that for a wide class of systems the new ingredient that enters is the Schwinger mechanism--the production of carriers from the vacuum by the applied field--which is then balanced against a scattering rate that is itself set by the field. We show by explicit computation how this works for the case of the symmetric superfluid-Mott insulator transition of bosons.

Phase bifurcation and quantum fluctuations in Sr3Ru2O7

The bilayer ruthenate Sr3Ru2O7 has been cited as a textbook example of itinerant metamagnetic quantum criticality. However, recent studies of the ultrapure system have revealed striking anomalies in magnetism and transport in the vicinity of the quantum critical point. Drawing on fresh experimental data, we show that the complex phase behavior reported here can be fully accommodated within the framework of a simple Landau theory. We discuss the potential physical mechanisms that underpin the phenomenology, and assess the capacity of the ruthenate system to realize quantum tricritial behavior.

Disorder-Sensitive Phase Formation Linked to Metamagnetic Quantum Criticality

Condensed systems of strongly interacting electrons are ideal for the study of quantum complexity. It has become possible to promote the formation of new quantum phases by explicitly tuning systems toward special low-temperature quantum critical points. So far, the clearest examples have been appearances of superconductivity near pressure-tuned antiferromagnetic quantum critical points. We present experimental evidence for the formation of a nonsuperconducting phase in the vicinity of a magnetic field-tuned quantum critical point in ultrapure crystals of the ruthenate metal Sr3Ru2O7, and we discuss the possibility that the observed phase is due to a spin-dependent symmetry-breaking Fermi surface distortion.

Effect of chromatic dispersion on nonlinear phase noise

We consider the combined effects of amplified spontaneous emission noise, optical Kerr nonlinearity, and chromatic dispersion on phase noise in an optical communication system. The effect of amplified spontaneous emission noise and Kerr nonlinearity were considered previously by Gordon and Mollenauer [Opt. Lett. 15, 1351 (1990)], and the effect of nonlinearity was found to be severe. We investigate the effect of chromatic dispersion on phase noise and show that it can either enhance or suppress the nonlinear noise amplification. For large absolute values of dispersion the nonlinear effect is suppressed, and the phase noise is reduced to its linear value. For a range of negative values of dispersion, however, nonlinear phase noise is enhanced and exhibits a maximum related to the modulation instability found in amplitude fluctuations. Nonlinear phase noise is quenched by these effects even in dispersion-compensated systems; the degree of suppression is sensitively dependent on the dispersion map. We demonstrate these results analytically with a simple linearized model.

Germline hMLH1 promoter mutation in a Newfoundland HNPCC kindred

Hereditary non-polyposis colon cancer (HNPCC) is an autosomal dominant form of inherited predisposition to colorectal and other malignancies. It is associated with mutations in DNA mismatch-repair genes, especially hMSH2 and hMLH1. Management of HNPCC families is improved if the underlying mutation in each family can be discovered. We describe a Newfoundland kindred, meeting the Amsterdam Criteria for HNPCC, in which a mutation in the promoter region of the hMLH1 gene co-segregates with the disease phenotype. The -42C > T mutation is within a putative Myb proto-oncogene binding site. Using electrophoretic mobility shift assays, we demonstrated that the mutated Myb binding sequence is less effective in binding nuclear proteins than the wild-type promoter sequence. Using in vivo transfection experiments in HeLa cells, we further demonstrated that the mutated promoter has only 37% of the activity of the wild-type promoter in driving the expression of a reporter gene. The average age of onset in six family members affected with colorectal cancer is 62 years, which is substantially later than the typical age of onset in HNPCC families. This is consistent with a substantial decrease, but not total elimination, of mismatch repair function in affected members of this family. This is the first report of a heritable hMLH1 promoter mutation in any HNPCC family.

Schrödinger equation with a spatially and temporally random potential: effects of cross-phase modulation in optical communication

We model the effects of cross-phase modulation in frequency (or wavelength) division multiplexed optical communications systems, using a Schrödinger equation with a spatially and temporally random potential. Green's functions for the propagation of light in this system are calculated using Feynman path-integral and diagrammatic techniques. This propagation leads to a non-Gaussian joint distribution of the input and output optical fields. We use these results to determine the amplitude and timing jitter of a signal pulse and to estimate the system capacity in analog communication.

Construct design for efficient, effective and high-throughput gene silencing in plants

Post-transcriptional silencing of plant genes using anti-sense or co-suppression constructs usually results in only a modest proportion of silenced individuals. Recent work has demonstrated the potential for constructs encoding self-complementary 'hairpin' RNA (hpRNA) to efficiently silence genes. In this study we examine design rules for efficient gene silencing, in terms of both the proportion of independent transgenic plants showing silencing, and the degree of silencing. Using hpRNA constructs containing sense/anti-sense arms ranging from 98 to 853 nt gave efficient silencing in a wide range of plant species, and inclusion of an intron in these constructs had a consistently enhancing effect. Intron-containing constructs (ihpRNA) generally gave 90-100% of independent transgenic plants showing silencing. The degree of silencing with these constructs was much greater than that obtained using either co-suppression or anti-sense constructs. We have made a generic vector, pHANNIBAL, that allows a simple, single PCR product from a gene of interest to be easily converted into a highly effective ihpRNA silencing construct. We have also created a high-throughput vector, pHELLSGATE, that should facilitate the cloning of gene libraries or large numbers of defined genes, such as those in EST collections, using an in vitro recombinase system. This system may facilitate the large-scale determination and discovery of plant gene functions in the same way as RNAi is being used to examine gene function in Caenorhabditis elegans.

High-oleic acid Australian Brassica napus and B. juncea varieties produced by co-suppression of endogenous Delta12-desaturases

Genetic engineering methods have been used successfully to modify the fatty acid profile of elite Australian germplasm of Brassica napus and B. juncea. Co-suppression plasmids carrying oleate desaturase genes from each species have been constructed and transferred into Australian elite breeding lines of B. napus and B. juncea using Agrobacterium tumifaciens plant-transformation techniques. Modifications to existing Brassica transformation protocols and the use of an intron-interrupted hygromycin-resistance gene as the selectable marker have resulted in improved transformation efficiencies. Silencing of the endogenous oleate desaturase genes has resulted in substantial increases in oleic acid levels, up to 89% in B. napus and 73% in B. juncea.

Feeling-of-knowing judgments and strategy selection in spelling

Metacognitive processes, such as monitoring one's knowledge and selecting appropriate strategies, may be important in skilled spelling. We hypothesized that skilled spellers have knowledge of which words they know how to spell and also that the accuracy with which people monitor their knowledge should be related to the spelling strategies they select. College students provided Feeling-of-Knowing ratings about the spellings of words and also spelled the same words and indicated whether they sounded out or remembered the spellings. Feeling-of-Knowing ratings were moderately correlated with Spelling Accuracy and were more strongly predictive of Spelling Accuracy when Feeling-of-Knowing ratings and spellings were done as part of the same task rather than as separate tasks. Analyses indicate that those who were better at monitoring their knowledge of spelling also chose more congruent spelling strategies. The results suggest that skilled spellers can monitor which words they know how to spell, but this ability to monitor is far from perfect and varies considerably. Further, the results suggest that ability to monitor spelling knowledge is related to strategy selection in spelling.

Regrets

A year or so ago I was invited by an Italian dentist to spend a day with him in his practice and to attend a two-day seminar, which he was presenting. The location, in the mountains near to Lake Como and the Swiss border, was enough to persuade me to accept. However I was to find out that the professional aspects of the trip were not only most invigorating but that they would also cause me to look back with concern to my own career. Had I done as well for my patients, my family and myself as I could have done?

Canadian immigration policy: the effectiveness of the point system and other instruments

"This paper examines the effects of changes in Canadian immigration policy on the occupational composition of immigration. We focus on 1967 changes that created a regulatory system, including the point system, that still forms the framework of Canadian immigration policy. We find that the point system provides some control over occupational composition but that its effectiveness in fine tuning is limited by the large number of other characteristics it seeks to control. We also find that entry class and source country composition of inflow have impacts that have swamped the effects of the point system in the last two decades." (SUMMARY IN FRE)

Insurance--a dental viewpoint. Part IV: Professional risks indemnity

Over the last decade professional practice has changed in many ways, not least in the willingness of patients to seek damages. The treasurer of the Medical Defence Union, in his report on the year 1989, stated that claims paid out on behalf of doctors in Britain doubled in frequency and the average amount awarded also doubled between 1985 and 1988, subscription rates increased fourfold. By contrast, 40 years ago life membership of a 'defence organisation' was available for less that an annual subscription today.

Insurance--a dental viewpoint. Part III: Life assurance, pensions and annuities

The insurance market is complex and there can be serious taxation implications in many decisions. The tax aspect may be beneficial to the dentist or it can have serious consequences. The advice of independent experts in accountancy and insurance is often vital if catastrophic pitfalls are to be avoided.

Insurance--a dental viewpoint. Part II: Sickness and accident

It is a very fortunate dentist indeed who survives an average 40-year working life without suffering illness or an accident. This will normally keep the dentist away from work and the ability to earn for a period of time. In the worst cases the disability may prevent a return to normal work with disastrous effects upon career earnings. Insurance against loss of earnings has therefore a very high priority.

Insurance--a dental viewpoint. Part I: An introduction

Current changes in the market are likely to alter our perception of insurance companies and brokers. Brokers will soon be required to disclose the amounts of commission earned and this may drive individuals back into the arms of the salesmen from individual companies. This series of articles sets out to show the options that are available to the dentist and to show how to use the range of expert advice available.

Biosynthesis of linolenate in developing embryos and cell-free preparations of high-linolenate linseed (Linum usitatissimum) and low-linolenate mutants

Biosynthesis of alpha-linolenate was investigated in developing embryos of the high-linolenic (45%) linseed cv. Glenelg, two mutant lines (M1589 and M1722) having reduced linolenic acid content (30%), and a very low linolenic (2%) genotype (Zero) obtained by recombination of the M1589 and M1722 mutations. Glenelg embryos showed an exponential rate of linolenate synthesis that paralleled their exponential pattern of triacylglycerol accumulation. The Zero line, although showing a pattern of triacylglycerol accumulation similar to that of Glenelg, accumulated linolenate at only a very low and constant rate throughout embryo development. An NADH- and O2-dependent decrease in oleate and increase in linolenate content of phosphatidylcholine was observed in dilute homogenates prepared from Glenelg embryos at 21 days after flowering, indicating active oleoyl- and linoleoyl-phosphatidylcholine desaturases in these preparations. While oleate decreased similarly in both sn positions of phosphatidylcholine, the increase in linolenate was confined mostly to the sn-2 position. Homogenates prepared from the mutant lines showed decreases in oleoyl-phosphatidylcholine similar to those of the wild-type Glenelg, whereas the increase in linolenoyl-phosphatidylcholine was substantially lower in M1589 and M1722 and barely detected in Zero. In vivo labeling experiments with detached embryos at 17 days after flowering, as well as analysis of endogenous linolenate content in various lipids, indicated that only delta 15-phospholipid desaturases, and not delta 15-galactolipid desaturases, were affected by the mutations. Embryos from M1722 had amounts of both radioactive and endogenous linolenate at position sn-1 of phosphatidylcholine that were close to those of the wild-type embryos, whereas M1589 had only 30 and 50% of these levels, respectively. The regulation of linolenic acid content in oilseeds is discussed on the basis of the results obtained.

Characterization of the seed and leaf lipids of high and low linolenic acid flax genotypes

The total seed lipids of four flax (Linum usitatissimum) genotypes, differing markedly in their acyl composition, were extracted and fractionated using column, preparative, and thin-layer chromatography. In the total lipid extract of seeds, the lower linolenate content of the cultivar Glenelg (39.1% compared to that of cv. Croxton (50.5%) was associated with a higher oleate content. Further reductions in linolenate content in the induced mutants of cv. Glenelg, M1722 (17.2%) and "Zero" (1.9%) were accompanied by equivalent increases in linoleate but only minor increases in oleate. Similar changes were observed in the major triacylglycerol fraction of the simple lipids (fatty acid esters of glycerol and sterols), but there was considerable heterogeneity for acyl composition in the minor simple lipid components, including both diacylglycerols and sterol esters, and the complex lipids (glycolipids and phospholipids). The induced mutations substantially reduced linolenate content of all lipid fractions but in no case was it eliminated. Maturation of "Zero" seed at 15/10 degrees C (compared to 24/19 degrees C) increased linoleate and decreased stearate and oleate contents in all lipid fractions. In contrast to seed lipids, the acyl composition of the leaf lipids of the mutant genotypes was the same as those of their parent.

Genetic control of polyunsaturated fatty acid biosynthesis in flax (Linum usitatissimum) seed oil

The inheritance of two mutants of flax (Linum usitatissimum), having altered proportions of the C18 polyunsaturated fatty acids, linoleic and linolenic, was examined. Both lines, 'M1589' and 'M1722', are homozygous for a single gene mutation which reduces linolenic acid content from 34% to 22% and raises linoleic acid from 15% to 27%. Genetic analysis of crosses involving 'M1589', 'M1722' and their parental cultivar 'Glenelg' revealed that these mutations are in different unlinked genes and exhibit additive (codominant) gene action. The symbolsLn1 andLn2 are proposed for the mutated genes in 'M1589' and 'M1722', respectively. Recombinant genotypes homozygous for the mutant alleles at both loci are very low in linolenic acid (2%) and high in linoleic acid (48%), with unaltered proportions of other fatty acids. The complete inverse correlation between linoleic and linolenic acids (r=-0.98) indicates that the mutations block the synthesis of linolenic acid at the linoleic desaturation step.

Inheritance of polyembryony in flax (Linum usitatissimum)

The inheritance of polyembryony (haploid–diploid twin seedlings) in the cross between Linum usitatissimum L. cv. Avantgarde (zero twinning) and cv. Rocket 4 (6.6% twins) was examined. It was concluded that the production of polyembryonic seeds is controlled mainly by additive gene action, with a realized narrow-sense heritability of 0.8. The frequency of twinning in the F2 generation displayed substantial transgressive segregation, ranging from zero to 32.0%. It was considered that such transgression could be due to either the presence of residual heterogeneity for twinning alleles in cv. Rocket 4, or the existence of a genetic system suppressing the expression of twinning alleles in cv. Avantgarde. The occurrence of a genotype producing haploid plants from more than 30% of its seeds should enable the efficiency of doubled-haploid line production to be greatly improved, and also lead to a better understanding of the embryological origins of the haploid component of polyembryonic seeds.

Variation for oil quantity and quality in linseed (Linum usitatissimum)

Significant variation in seed weight, oil content and fatty acid composition was found both between and within varieties in a diverse collection of 214 Linum usitatissimum accessions. Parent-offspring correlation analysis indicated that at least a proportion of the variation within several varieties was due to genetic heterogeneity. Lines were identified that had up to 46 % oil, compared with the 40 % present in the current Australian cultivar, Glenelg. High oil content was consistently associated with larger seeds. Oleic acid and linolenic acid varied between 13.3 and 25.2%, and 45.5 and 64.2 %, respectively, and were strongly negatively correlated within and between all varieties tested. The level of variation is insufficient to develop lines with less than 5 % linolenic acid by conventional hybridization and selection techniques. It is concluded that mutation breeding and interspecific hybridization are more promising approaches to the breeding of linseed genotypes containing low levels of linolenic acid.

Effect of FPL57787 in exercise-induced asthma

In ten patients with extrinsic asthma the effects of a new oral chromone FPL57787 and placebo were studied in a random double-blind fashion to assess the effect of FPL57787 in preventing exercise-induced asthma (EIA). Exercise testing consisted of steady state running on an inclined treadmill for up to 8 min. FPL57787 gave significant protection (P less 0.01) compared to placebo from the maximum percentage fall in FEV1, FVC and MMEF after exercise. FPL57787 also produced a small but significant (P less than 0.01) percentage increase in FEV1 2 hr after the drug compared to placebo, whereas no significant increase was seen in FVC or in MMEF.

Cell-mediated immunity in operable bronchial carcinoma: the effect of injecting irradiated autologous tumour cells and BCG

In 52 patients undergoing tests of cell-mediated immunity before surgical resection of bronchial carcinoma a positive tuberculin test result was found in 71% compared with 68% of age- and sex-matched controls. Sensitisation to DNCB occurred in 52% of 37 patients but in 78% of controls. There was depression of lymphocyte transformation by PPD in 19 patients compared with controls (P=0.001), but there was no difference in lymphocyte transformation by PHA or pokeweed mitogen between 34 patients and controls. In a pilot study patients were randomly allocated to autograft (eight) or non-autograft (seven) groups. The autograft group were given an intradermal injection of a suspension of irradiated autologous tumour-cells mixed with intradermal BCG on the day of operation. Tests of cell-mediated immunity were repeated two weeks after operation. Five patients in each group received a course of radiotherapy to the mediastinum three weeks after operation. There was a rise in cutaneous tuberculin reactivity (P=0.08) and total leucocyte count (P=0.09) in the autograft group postoperatively with a fall in total lymphocyte and T lymphocyte counts in the non-autograft group (P less 0.05). These differences, however, were not followed by any difference in the frequency of tumour recurrence or the survival rate two years after operation. The results show that the immunological surveillance mechanism is impaired even in patients with early bronchial carcinoma and that it is possible to overcome postoperative immunological depression with specific immunotherapy combined with BCG. This treatment did not produce any clinical advantage in this small number of patients and the skin lesions caused the patients considerable discomfort.

Disopyramide--an effective treatment for lignocaine resistant ventricular dysrhythmias

Intravenous disopyramide was used in 13 patients who developed recurrent ventricular dysrhythmias despite initial treatment with intravenous lignocaine after admission to the Coronary Care Unit of a busy district hospital. This was effective in 8 of the 13 patients treated and there was no major side effects observed. Disopyramide has the advantage of being available both as an oral and an intravenous preparation and is a useful drug to be added to the list of more conventional anti-dysrhythmic agents.