2,335 research outputs found
Comments on the PLA article 'UCN anomalous losses and the UCN capture cross section on material defects' [Phys. Lett. A 335 (2005) 327]
We comment on the paper `UCN anomalous losses and the UCN capture cross
section on material defects' by A. Serebrov et al., Phys. Lett. A 335 (2005)
327 - 336. Data presented do not originate from these authors alone but were
taken in collaboration with several other authors and institutes not mentioned.Comment: 4 page
ACSys/RDN experiences with Telstra’s experimental broadband network, first progress report
This report summarises our experiences with the EBN and provides an indication of where we are now. We don’t present a set of detailed performance measurements in this report, instead we focus primarily on bandwidth utilisation and network management. We are currently producing a more comprehensive set of performance measurements, which will be presented in a subsequent report
Role of carbon dioxide and ion transport in the formation of sub-embryonic fluid by the blastoderm of the Japanese quail
1. The explanted blastoderm of the Japanese quail was used to explore the role of ions and carbon dioxide in determining the rate of sub-embryonic fluid (SEF) production between 54 and 72 h of incubation.
2. Amiloride, an inhibitor of Na+/H+ exchange, at concentrations of 10-3 to 10-6 M substantially decreased the rate of SEF production when added to the albumen culture medium. N-ethylmaleimide, an inhibitor of V type H+ ATPase, also decreased this rate but only to a small extent at the highest dose applied, 10-3 M. Both inhibitors had no effect on SEF production when added to the SEF. 3. The inhibitors of cellular bicarbonate and chloride exchange, 4-acetamido-4-'isothiocyano-2, 2-'disulphonic acid (SITS) and 4,4'diisothiocyanostilbene-2,2-'disulphonic acid (DIDS), had no effect upon SEF production.
4. Ouabain, an inhibitor of Na+/K+ ATPase, decreased SEF production substantially at all concentrations added to the SEF (10-3 to 10-6 M). Three sulphonamide inhibitors of carbonic anhydrase, acetazolamide, ethoxzolamide and benzolamide, decreased SEF production when added to the SEF at concentrations of 10-3 to 10-6 M. Benzolamide was by far the most potent. Neither ouabain nor the sulphonamides altered SEF production when added to the albumen culture medium.
5. Using a cobalt precipitation method, carbonic anhydrase activity was localised to the endodermal cells of the area vasculosa. The carbonic anhydrase activity was primarily associated with the lateral plasma membranes, which together with the potent inhibitory effect of benzolamide, suggests the carbonic anhydrase of these cells is the membrane-associated form, CA IV.
6. The changes in SEF composition produced by inhibitors were consistent with the production of SEF by local osmotic gradients.
7. It is concluded that a Na+/K+ ATPase is located on the basolateral membranes of the endodermal cells of the area vasculosa , and that a sodium ion/hydrogen ion exchanger is located on their apical surfaces. Protons for this exchanger would be provided by the hydration of CO2 catalysed by the membrane-associated carbonic anhydrase. Furthermore, it is proposed that the prime function of the endodermal cells of the area vasculosa is the production of SEF
Causal explanation for observed superluminal behavior of microwave propagation in free space
In this paper we present a theoretical analysis of an experiment by Mugnai
and collaborators where superluminal behavior was observed in the propagation
of microwaves. We suggest that what was observed can be well approximated by
the motion of a superluminal X wave. Furthermore the experimental results are
also explained by the so called scissor effect which occurs with the
convergence of pairs of signals coming from opposite points of an annular
region of the mirror and forming an interference peak on the intersection axis
traveling at superluminal speed. We clarify some misunderstandings concerning
this kind of electromagnetic wave propagation in vacuum.Comment: 9 pages, 3 figures, accepted for publication in Physics Letters
Landau and dynamical instabilities of Bose-Einstein condensates with superfluid flow in a Kronig-Penney potential
We study the elementary excitations of Bose-Einstein condensates in a
one-dimensional periodic potential and discuss the stability of superfluid flow
based on the Kronig-Penney model. We analytically solve the Bogoliubov
equations and calculate the excitation spectrum. The Landau and dynamical
instabilities occur in the first condensate band when the superfluid velocity
exceeds certain critical values, which agrees with the result of condensates in
a sinusoidal potential. It is found that the onset of the Landau instability
coincides with the point where the perfect transmission of low-energy
excitations is forbidden, while the dynamical instability occurs when the
effective mass is negative. It is well known that the condensate band has a
peculiar structure called swallowtail when the periodic potential is shallow
compared to the mean field energy. We find that the upper side of the
swallowtail is dynamically unstable although the excitations have the linear
dispersion reflecting the positive effective mass.Comment: 6 pages, 2 figures, Proceedings of the International Symposium on
Quantum Fluids and Solids (QFS2006
Alternative approach to in the uMSSM
The gluino contributions to the Wilson coefficients for are calculated within the unconstrained MSSM. New stringent bounds on
the and mass insertion parameters are
obtained in the limit in which the SM and SUSY contributions to
approximately cancel. Such a cancellation can plausibly appear within several
classes of SUSY breaking models in which the trilinear couplings exhibit a
factorized structure proportional to the Yukawa matrices. Assuming this
cancellation takes place, we perform an analysis of the decay. We
show that in a supersymmetric world such an alternative is reasonable and it is
possible to saturate the branching ratio and produce a CP
asymmetry of up to 20%, from only the gluino contribution to
coefficients. Using photon polarization a LR asymmetry can be defined that in
principle allows for the and contributions to the decay to be disentangled. In this scenario no constraints on the ``sign
of '' can be derived.Comment: LaTeX2e, 23 pages, 7 ps figure, needs package epsfi
Novel 4, 8-benzobisthiazole copolymers and their field-effect transistor and photovoltaic applications
A series of copolymers containing the benzo[1,2-d:4,5-d′]bis(thiazole) (BBT) unit has been designed and synthesised with bisthienyl-diketopyrrolopyrrole (DPP), dithienopyrrole (DTP), benzothiadiazole (BT), benzodithiophene (BDT) or 4,4′-dialkoxybithiazole (BTz) comonomers. The resulting polymers possess a conjugation pathway that is orthogonal to the more usual substitution pathway through the 2,6-positions of the BBT unit, facilitating intramolecular non-covalent interactions between strategically placed heteroatoms of neighbouring monomer units. Such interactions enable a control over the degree of planarity through altering their number and strength, in turn allowing for tuning of the band gap. The resulting 4,8-BBT materials gave enhanced mobility in p-type organic field-effect transistors of up to 2.16 × 10−2 cm2 V−1 s−1 for pDPP2ThBBT and good solar cell performance of up to 4.45% power conversion efficiency for pBT2ThBBT
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