The South African estuarine specialist Codium tenue (Bryopsidales, Chlorophyta) discovered in a south-western Australian estuary

Codium tenue, previously known reliably only from estuarine habitats in South Africa, is recorded from a similar habitat in the Walpole and Nornalup Inlet system, on the south coast of Western Australia. The Australian C. tenue has a repeatedly divaricately dichotomously branched thallus to 11.5 cm in height, with markedly compressed axes up to 1 cm in width at branch dichotomies, but distally attenuating to terete branch apices. Structurally, thalli have cortices with distinctive cuneate utricles up to 1310 μm long and 650 μm in diameter. Both the habit and structural morphology essentially agree with C. tenue as known in South Africa. Sequences generated from the Australian specimens are also wholly comparable with those of South African specimens newly generated in this study. While similarly disjunct South African/Western Australian distributions are known for other algae, that of C. tenue is particularly remarkable in that the species is apparently an estuarine specialist

On-chip resonantly-driven quantum emitter with enhanced coherence

Advances in nanotechnology provide techniques for the realisation of integrated quantum-optical circuits for on-chip quantum information processing(QIP). The indistinguishable single photons, required for such devices can be generated by parametric down-conversion, or from quantum emitters such as colour centres and quantum dots(QDs). Among these, semiconductor QDs offer distinctive capabilities including on-demand operation, coherent control, frequency tuning and compatibility with semiconductor nanotechnology. Moreover, the coherence of QD photons can be significantly enhanced in resonance fluorescence(RF) approaching at its best the coherence of the excitation laser. However, the implementation of QD RF in scalable on-chip geometries remains challenging due to the need to suppress stray laser photons. Here we report on-chip QD RF coupled into a single-mode waveguide with negligible resonant laser background and show that the coherence is enhanced compared to off-resonant excitation. The results pave the way to a novel class of integrated quantum-optical devices for on-chip QIP with embedded resonantly-driven quantum emitters

On-chip resonantly-driven quantum emitter with enhanced coherence

Advances in nanotechnology provide techniques for the realisation of integrated quantum-optical circuits for on-chip quantum information processing(QIP). The indistinguishable single photons, required for such devices can be generated by parametric down-conversion, or from quantum emitters such as colour centres and quantum dots(QDs). Among these, semiconductor QDs offer distinctive capabilities including on-demand operation, coherent control, frequency tuning and compatibility with semiconductor nanotechnology. Moreover, the coherence of QD photons can be significantly enhanced in resonance fluorescence(RF) approaching at its best the coherence of the excitation laser. However, the implementation of QD RF in scalable on-chip geometries remains challenging due to the need to suppress stray laser photons. Here we report on-chip QD RF coupled into a single-mode waveguide with negligible resonant laser background and show that the coherence is enhanced compared to off-resonant excitation. The results pave the way to a novel class of integrated quantum-optical devices for on-chip QIP with embedded resonantly-driven quantum emitters

Observation of two relaxation mechanisms in transport between spin split edge states at high imbalance

Using a quasi-Corbino geometry to directly study electron transport between spin-split edge states, we find a pronounced hysteresis in the I-V curves, originating from slow relaxation processes. We attribute this long-time relaxation to the formation of a dynamic nuclear polarization near the sample edge. The determined characteristic relaxation times are 25 s and 200 s which points to the presence of two different relaxation mechanisms. The two time constants are ascribed to the formation of a local nuclear polarization due to flip-flop processes and the diffusion of nuclear spins.Comment: Submitted to PR

Direct seeding of chenopod shrubs for saltland and rangeland environments

There are currently two ways of establishing chenopod shrubs: sowing from seed using a niche seeder, or planting nursery-raised seedlings with a tree planter. Planting seedlings is the more reliable method, but is relatively expensive (in excess of $450 per hectare). On the other hand, direct seeding using the specialised “niche seeder” is much less expensive ($100-150 per hectare), but is also less reliable. This project aimed to investigate alternative methods of direct seeding chenopod shrubs for saltland and rangeland areas by developing a greater understanding of their seed biology and agronomic requirements. Our aspiration was that shrubs should be established using more conventional farm machinery. This bulletin reports on a combination of seed biology and agronomic research to develop reliable, low-cost direct seeding options for chenopod shrubs. Experiments into the impact of changing environmental conditions on seeds were studied in the laboratory, and field experiments were conducted to test the applicability of these insights in the field using conventional modified farm seeding machinery. As a result of this work, a successful direct seeding package using farm seeding equipment (modified for wide row spacings and depth control) was developed for Atriplex nummularia (old man saltbush), the most widely planted saltbush species across southern Australia. The nine key elements of the package are: 1. Select suitable paddocks for introduction of new shrubs 2. Prepare a weed-free seedbed using two knockdown herbicide applications (4-6 weeks and 1-2 weeks before seeding) and commence control of rabbits and kangaroos 3. Sow the best seed, by ensuring: a. Large fruits, with a high proportion of viable seeds, have been selected b. Seed is of subspecies nummularia (not subsp. spathulata) c. Fruits have been harvested within the previous six months and stored in a cool, dry environment d. Bracts are retained around the seeds 4. Sow into moisture in late winter - early spring (depending on district) a. If the area to be sown is waterlogged, defer sowing until later in spring b. If insufficient soil moisture, defer sowing until the following year 5. Use a sowing rate of ~10 fruits/m (if germination rate is 15%) to provide at least one plant for every 2 m of row; use higher rates for seed of lower germination 6. Set the seeder up to sow into furrows with trailing press wheels 7. Sow to a depth of 5-10 mm (very critical) 8. Control weeds and pests (insects, mites, kangaroos and rabbits) 9. Defer grazing until seedlings are well established This establishment method has also been shown to work for Rhagodia preissii (mallee saltbush). This project was not able to develop reliable direct seeding packages for other Atriplex species, including A. amnicola and A. undulata. Further work is needed to understand the triggers for their germination, before these species can be direct-seeded with conventional machinery. Direct sowing of M. brevifolia and M. pyramidata appears to be problematic in much of southern Australia, due to their requirement for temperatures >30°C for germination, which do not occur within the normal winter growing season. An exception to this would be areas with more reliable summer rainfall, such as northern New South Wales, where sowing could be deferred until late spring-early summer. An alternative strategy for establishing M. brevifolia, is to encourage natural recruitment of seedlings from seed produced on surrounding bushes (if it is already present in the area), or to transplant a low density of nursery-raised seedlings, which could then act as a seed source for natural recruitment (if it is not already present)

Two-Loop g -> gg Splitting Amplitudes in QCD

Splitting amplitudes are universal functions governing the collinear behavior of scattering amplitudes for massless particles. We compute the two-loop g -> gg splitting amplitudes in QCD, N=1, and N=4 super-Yang-Mills theories, which describe the limits of two-loop n-point amplitudes where two gluon momenta become parallel. They also represent an ingredient in a direct x-space computation of DGLAP evolution kernels at next-to-next-to-leading order. To obtain the splitting amplitudes, we use the unitarity sewing method. In contrast to the usual light-cone gauge treatment, our calculation does not rely on the principal-value or Mandelstam-Leibbrandt prescriptions, even though the loop integrals contain some of the denominators typically encountered in light-cone gauge. We reduce the integrals to a set of 13 master integrals using integration-by-parts and Lorentz invariance identities. The master integrals are computed with the aid of differential equations in the splitting momentum fraction z. The epsilon-poles of the splitting amplitudes are consistent with a formula due to Catani for the infrared singularities of two-loop scattering amplitudes. This consistency essentially provides an inductive proof of Catani's formula, as well as an ansatz for previously-unknown 1/epsilon pole terms having non-trivial color structure. Finite terms in the splitting amplitudes determine the collinear behavior of finite remainders in this formula.Comment: 100 pages, 33 figures. Added remarks about leading-transcendentality argument of hep-th/0404092, and additional explanation of cut-reconstruction uniquenes

The use of incidence counts for estimation of cereal aphid populations. 3. Population development and the incidence-density relation.

Om in de praktijk gebruik te kunnen maken van incidentie (de fractie bezette halmen) voor het schatten van graanluispopulaties moet dezelfde relatie tussen dichtheid en incidentie tijdens het hele groeiseizoen gelden. Uit analyses van veldgegevens voor de graanluis Sitobion avenae blijkt dat wel het geval te zijn, zodat bepalingen van incidentie kunnen worden gebruikt om de populatiedichtheid betrouwbaar te schatte

Inherited Twistor-Space Structure of Gravity Loop Amplitudes

At tree-level, gravity amplitudes are obtainable directly from gauge theory amplitudes via the Kawai, Lewellen and Tye closed-open string relations. We explain how the unitarity method allows us to use these relations to obtain coefficients of box integrals appearing in one-loop N=8 supergravity amplitudes from the recent computation of the coefficients for N=4 super-Yang-Mills non-maximally-helicity-violating amplitudes. We argue from factorisation that these box coefficients determine the one-loop N=8 supergravity amplitudes, although this remains to be proven. We also show that twistor-space properties of the N=8 supergravity amplitudes are inherited from the corresponding properties of N=4 super-Yang-Mills theory. We give a number of examples illustrating these ideas.Comment: 32 pages, minor typos correcte

From Trees to Loops and Back

We argue that generic one-loop scattering amplitudes in supersymmetric Yang-Mills theories can be computed equivalently with MHV diagrams or with Feynman diagrams. We first present a general proof of the covariance of one-loop non-MHV amplitudes obtained from MHV diagrams. This proof relies only on the local character in Minkowski space of MHV vertices and on an application of the Feynman Tree Theorem. We then show that the discontinuities of one-loop scattering amplitudes computed with MHV diagrams are precisely the same as those computed with standard methods. Furthermore, we analyse collinear limits and soft limits of generic non-MHV amplitudes in supersymmetric Yang-Mills theories with one-loop MHV diagrams. In particular, we find a simple explicit derivation of the universal one-loop splitting functions in supersymmetric Yang-Mills theories to all orders in the dimensional regularisation parameter, which is in complete agreement with known results. Finally, we present concrete and illustrative applications of Feynman's Tree Theorem to one-loop MHV diagrams as well as to one-loop Feynman diagrams.Comment: 52 pages, 17 figures. Some typos in Appendix A correcte

Behavioral interactions between opiate and antiepileptic drugs in the mouse

Morphine and related opioid compounds are known to possess proconvulsant activity based upon both electroencephalographic and behavioral criteria. The present authors previously suggested that opiate-related seizures were behaviorally inhibitory, and this was further investigated in the present study. The effects of pretreatment with three pharmacologically distinct compounds (sodium valproic acid, trimethadione, taurine) upon normal behavioral activation to systemic morphine were examined in the mouse. Morphine consistently increased activity levels in comparison with vehicle. Each of the three experimental compounds itself was behaviorally inhibitory; nonetheless both sodium valproate and trimethadione facilitated behavioral responses to morphine. The effects of the same drugs upon activation produced by central administration of a long-lasting enkephalin analog (-ala2-leu-enkephalinamide) were investigated, with similar results. These findings confirm a behavioral interaction between opiate and anticonvulsant drugs, although it may be selective for certain classes of anticonvulsant compounds.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24414/1/0000684.pd