1,081 research outputs found
Flowering and vegetative propagation of pyrethrum (Chrysanthemum cinerariaefolium Vis.) in vivo and in vitro
The influence of climatic conditions was investigated on flowering behaviour of pyrethrum ( Chrysanthemum cinerariaefolium Vis.). At low temperatures high numbers of plants initiated high numbers of flower heads. Both the development of the initiated flower heads and the vegetative development of the plants were stimulated by higher temperatures.The second aspect was the development of methods of vegetative propagation in vivo and in vitro. Through a culture of peduncle explants in vitro detailed information was obtained about the initiation and development of adventitious roots. With these data the process of adventitious root formation of shoot cuttings in vivo was optimalized. In practice this method of vegetative propagation in vivo may be useful for a fast multiplication of selected healthy plants with high yields of pyrethrins. Vegetative propagation was also achieved by initiation and development of adventitious shoots on capitulum explants cultivated in vitro and subsequent adventitious root formation of detached shoots. This procedure was applicable for vegetative propagation of several other Compositae.</em
Generalized mirror symmetry and trace anomalies
We consider compactification of M-theory on X7 with betti numbers (b_0, b_1,
b_2, b_3, b_3, b_2, b_1, b_0) and define a generalized mirror symmetry (b_0,
b_1, b_2, b_3) goes to (b_0, b_1, b_2 -rho/2, b_3+rho/2)$ under which rho =
7b_0-5b_1+3b_2 -b_3 changes sign. Generalized self-mirror theories with rho=0
have massless sectors with vanishing trace anomaly (before dualization).
Examples include pure supergravity with N \geq 4 and supergravity plus matter
with N \leq 4.Comment: 19 pages late
Analysis of Coplanar On-Chip Interconnects on Lossy Semiconducting Substrates
In this paper, a method for analysis and modeling of coplanar transmission interconnect lines that are placed on top of silicon-silicon oxide substrates is presented. The potential function is expressed by series expansions in terms of solutions of the Laplace equation for each homogeneous region of layered structure. The expansion coefficients of different series are related to each other and to potentials applied to the conductors via boundary conditions. In the plane of conductors, boundary conditions are satisfied at Nd discrete points with Nd being equal to the number of terms in the series expansions. The resulting system of inhomogeneous linear equations is solved by matrix inversion. No iterations are required. A discussion of the calculated line admittance parameters as functions of width of conductors, thickness of the layers, and frequency is given. The interconnect capacitance and conductance per unit length results are given and compared with those obtained using full wave solutions, and good agreement have been obtained in all the cases treated
Efficient single-photon emission from electrically driven InP quantum dots epitaxially grown on Si(001)
The heteroepitaxy of III-V semiconductors on silicon is a promising approach
for making silicon a photonic platform for on-chip optical interconnects and
quantum optical applications. Monolithic integration of both material systems
is a long-time challenge, since different material properties lead to high
defect densities in the epitaxial layers. In recent years, nanostructures
however have shown to be suitable for successfully realising light emitters on
silicon, taking advantage of their geometry. Facet edges and sidewalls can
minimise or eliminate the formation of dislocations, and due to the reduced
contact area, nanostructures are little affected by dislocation networks. Here
we demonstrate the potential of indium phosphide quantum dots as efficient
light emitters on CMOS-compatible silicon substrates, with luminescence
characteristics comparable to mature devices realised on III-V substrates. For
the first time, electrically driven single-photon emission on silicon is
presented, meeting the wavelength range of silicon avalanche photo diodes'
highest detection efficiency
Vanishing Preons in the Fifth Dimension
We examine supersymmetric solutions of N=2, D=5 gauged supergravity coupled
to an arbitrary number of abelian vector multiplets using the spinorial
geometry method. By making use of methods developed in hep-th/0606049 to
analyse preons in type IIB supergravity, we show that there are no solutions
preserving exactly 3/4 of the supersymmetry.Comment: 19 pages, latex. Reference added, and further modification to the
introductio
UV constraints on massive spinning particles: lessons from the gravitino
Self-interacting massive particles with spin unavoidably violate
unitarity; the question is at what scale. For spin- the strong coupling
scale (at which perturbative unitarity is lost) cannot be raised by any finite
tuning of the interactions, while for spin- there exists a special tuning of
the Wilson coefficients which can raise this scale (and enjoys numerous special
properties such as ghost-freedom). Here, we fill in the missing piece by
describing how the self-interactions of a massive spin- field, or "massive
gravitino", become strongly coupled at high energies. We show that while
several different structures appear in the leading order potential, the strong
coupling scale cannot be raised (in the absence of additional fields). At the
level of the off-shell Lagrangian, it is always the non-linear symmetries of
the longitudinal Stuckelberg mode that dictate the strong coupling, and we show
that in general it is only possible to parametrically raise the strong coupling
scale if Wess-Zumino structures exist. We complement this off-shell approach
with a first analysis of positivity bounds for a massive spin- particle,
showing that any potential self-interaction which contributes to an on-shell
2-to-2 elastic process at tree level must vanish if this low-energy theory is
to have a standard UV completion. We identify the mixing between the
longitudinal mode and the transverse modes as the main obstacle to positivity,
and clarify how the non-Abelian nature of non-linear (dRGT) massive gravity
allows it to satisfy positivity where all known spin Abelian
theories fail. Our results imply that a massive gravitino cannot appear alone
in a controlled EFT---it must be accompanied by other particles, e.g.~as part
of a supermultiplet. Together with the spin- and spin- cases, we suggest
features which will persist in even higher spin massive theories
Non-extremal D-instantons
We construct the most general non-extremal deformation of the D-instanton
solution with maximal rotational symmetry. The general non-supersymmetric
solution carries electric charges of the SL(2,R) symmetry, which correspond to
each of the three conjugacy classes of SL(2,R). Our calculations naturally
generalise to arbitrary dimensions and arbitrary dilaton couplings.
We show that for specific values of the dilaton coupling parameter, the
non-extremal instanton solutions can be viewed as wormholes of non-extremal
Reissner-Nordstr\"om black holes in one higher dimension. We extend this result
by showing that for other values of the dilaton coupling parameter, the
non-extremal instanton solutions can be uplifted to non-extremal non-dilatonic
p-branes in p+1 dimensions higher.
Finally, we attempt to consider the solutions as instantons of (compactified)
type IIB superstring theory. In particular, we derive an elegant formula for
the instanton action. We conjecture that the non-extremal D-instantons can
contribute to the R^8-terms in the type IIB string effective action.Comment: 31 pages, 4 figures. v3: minor correction and reference adde
Presence of Coxiella burnetii DNA in inflamed bovine cardiac valves
Background: Bacterial endocarditis is a recognised disease in humans and animals. In humans, infection with Coxiella burnetii can cause endocarditis, but this has not been investigated thoroughly in animals. Endocarditis in cattle is a common post-mortem finding in abattoirs and studies have identified Trueperella pyogenes as a major cause. Despite exposure of cattle to C. burnetii, the significance of this particular bacterium for development and progression of endocarditis has not been studied in detail. Cardiac valves of cattle affected with endocarditis (n = 100) were examined by histology, fluorescence in situ hybridization (FISH) and real time quantitative polymerase chain reaction (PCR). Serum was examined for anti-C. burnetii antibodies by enzyme-linked immunosorbent assay (ELISA). Results: Serology revealed that 70% of the cattle were positive for antibodies to C. burnetii, while PCR analysis identified 25% of endocarditis valve samples as being positive. C. burnetii was not detected by FISH, probably due to the low infection levels. Most cattle had chronic valvular vegetative endocarditis with lesions being characterised by a core of fibrous tissue covered by significant amounts of fibrin, sometimes with areas of liquefaction, and with a coagulum covering the surface. In a few cases, including the case with the highest infection level, lesions were characterized by extensive fibrosis and calcification. Histologically, bacteria other than C. burnetii were observed in most cases. Conclusions: The presence of C. burnetii DNA is relatively common in cattle affected with valvular endocarditis. The role of C. burnetii remains however unknown as lesions did not differ between C. burnetii infected and non-infected cattle and because T. pyogenes-like bacteria were present in the inflamed valves; a bacterium able to induce the observed lesions. Heart valves of normal cattle should be investigated to assess if C. burnetii may be present without preexisting lesions.</p
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