Reply to Comment on Dirac spectral sum rules for QCD in three dimensions

I reply to the comment by Dr S. Nishigaki (hep-th/0007042) to my papers Phys. Rev. D61 (2000) 056005 and Phys. Rev. D62 (2000) 016005.Comment: 2 pages, LaTeX, no figure

Comment on "Nucleon elastic form factors and local duality"

We comment on the papers "Nucleon elastic form factors and local duality" [Phys. Rev. {\bf D62}, 073008 (2000)] and "Experimental verification of quark-hadron duality" [Phys. Rev. Lett. {\bf 85}, 1186 (2000)]. Our main comment is that the reconstruction of the proton magnetic form factor, claimed to be obtained from the inelastic scaling curve thanks to parton-hadron local duality, is affected by an artifact.Comment: to appear in Phys. Rev.

Self-protection and insurance with interdependencies

We study optimal investment in self-protection of insured individuals when they face interdependencies in the form of potential contamination from others. If individuals cannot coordinate their actions, then the positive externality of investing in self-protection implies that, in equilibrium, individuals underinvest in self-protection. Limiting insurance coverage through deductibles or selling “at-fault” insurance can partially internalize this externality and thereby improve individual and social welfare. JEL Classification: C72, D62, D8

H2O Maser Observations of Candidate Post-AGB Stars and Discovery of Three High-velocity Water Sources

We present the results of 22 GHz H_2O maser observations of a sample of 85 post-Asymptotic Giant Branch (post-AGB) candidate stars, selected on the basis of their OH 1612 MHz maser and far-infrared properties. All sources were observed with the Tidbinbilla 70-m radio telescope and 21 detections were made. 86 GHz SiO Mopra observations of a subset of the sample are also presented. Of the 21 H_2O detections, 15 are from sources that are likely to be massive AGB stars and most of these show typical, regular H_2O maser profiles. In contrast, nearly all the detections of more evolved stars exhibited high-velocity H_2O maser emission. Of the five sources seen, v223 (W43A, IRAS 18450-0148) is a well known `water-fountain' source which belongs to a small group of post-AGB stars with highly collimated, high-velocity H_2O maser emission. A second source in our sample, v270 (IRAS 18596+0315), is also known to have high-velocity emission. We report the discovery of similar emission from a further three sources, d46 (IRAS 15445-5449), d62 (IRAS 15544-5332) and b292 (IRAS 18043-2116). The source d46 is an evolved post-AGB star with highly unusual maser properties. The H_2O maser emission from d62 is probably associated with a massive star. The source b292 is a young post-AGB star that is highly likely to be a water-fountain source, with masers detected over a velocity range of 210 km s^{-1}.Comment: 47 pages, 9 figures, 4 tables, accepted by Ap

Bioeconomics of Sustainable Harvest of Competing Species: A Comment

We refer to Flaaten’s (JEEM 1991, pp. 163–80) study on competing species. In Theorem 5 (Theorem 6), Flaaten claims that a higher price (harvesting costs) of one species yields a lower (greater) own stock-size and a greater (lower) stock-size of the competing species in the steady state. It is shown that both claims are wrong.Renewable resources, fishery management, multiple species model, Resource /Energy Economics and Policy, D62, D99, Q22,

Supersymmetric Composite Models on Intersecting D-branes

We construct supersymmetric composite models of quarks and leptons from type IIA T^6/(Z_2 x Z_2) orientifolds with intersecting D6-branes. In case of T^6 = T^2 x T^2 x T^2 with no tilted T^2, a composite model of the supersymmetric SU(5) grand unified theory with three generations is constructed. In case of that one T^2 is tilted, a composite model with SU(3)_c x SU(2)_L x U(1)_Y gauge symmetry with three generations is constructed. These models are not realistic, but contain fewer additional exotic particles and U(1) gauge symmetries due to the introduction of the compositeness of quarks and leptons. The masses of some exotic particles are naturally generated through the Yukawa interactions among "preons".Comment: 15 pages, 2 figure

Dynamical Generation of Yukawa Interactions in Intersecting D-brane Models

We construct a supersymmetric composite model in type IIA T^6/(Z_2 x Z_2) orientifold with intersecting D6-branes. Four generations of quarks and leptons are naturally emerged as composite fields at low energies. Two pairs of light electroweak Higgs doublets are also naturally obtained. The hierarchical Yukawa couplings for the quark-lepton masses can be generated by the interplay between the string-level higher dimensional interactions among "preons" and the dynamics of the confinement of "preons". Besides having four generations of quarks and leptons, the model is not realistic in some points: some exotic particles, one additional U(1) gauge symmetry, no explicit mechanism for supersymmetry breaking, and so on. This model is a toy model to illustrate a new mechanism of dynamical generation of Yukawa couplings for the masses and mixings of quarks and leptons.Comment: 18 pages, 6 figure

The use of enzymes, isomerisable lipid analogues and small molecules to modulate the structure and dynamics of lipid bilayer

A series of experiments were carried out to assess the effects and interactions of isomerisable lipid analogues, small molecules, and enzyme catalysed substrates on the structure and dynamics of lipid bilayers. Modulation of Enzyme Activity Using an Azobenzene-Containing Lipid Analogue – An azobenzene-containing phosphocholine lipid analogue (bis-Azo-PC) was synthesised and incorporated into 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposomes containing diacylglycerol kinase (DGK) in order to assess the effect of photoisomerisation of the azobenzene group on the activity of the protein. The increase in volume of bis-Azo-PC in the cis state should have a significant effect on protein activity as bilayer tension increases. Protein activity was measured using an enzyme activity assay. The difference in specific activity between the trans and cis states of the azobenzene was too small to discern a significant effect on protein activity. Lipid Phase Behaviour – The phase behaviour of 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine-d62 (d62-DPPC) samples containing cholesterol and the serotonin receptor agonist drugs quipazine and LY-165,135 was analysed using proton and deuterium NMR spectroscopy and differential scanning calorimetry (DSC). The effect of quipazine and LY-165,135 on d62-DPPC was an elongation of the gel-to-fluid lamellar phase transition, lowering of the start of the phase transition, and disappearance of the ripple phase observed in d62-DPPC alone. The effect of cholesterol on d62-DPPC was a smoothing of the phase transition due to the presence of the liquid-ordered phase. Spectra of d62-DPPC, cholesterol and quipazine also show the presence of the liquid-ordered phase. Spectra of d62-DPPC and cholesterol with LY-165,135 show that the drug widens the temperature range over which the liquid-ordered phase exists. These results indicate that the presence of small molecules such as serotonin-receptor agonists can have a significant effect on the phase behaviour of the lipid bilayer. Analysis of Drug Localisation and Orientation in a Model Membrane by NMR Spectroscopic Methods – NOESY cross-relaxation rates were used to generate location probabilities for serotonin-receptor agonist drugs in d62-DPPC bilayers with and without cholesterol. Both drugs were found to locate in the interface region of the bilayer, although they had difference orientations relative to the bilayer normal; quipazine was oriented parallel to the d62-DPPC molecules, while LY-165,135 was oriented perpendicular to the lipid. The presence of cholesterol was found to affect the drugs‟ positions in the bilayer. Quipazine was pushed further towards the centre of the bilayer (the acyl chain termini) when the sample was in the fluid lamellar phase. The effect on LY-165,135, conversely, was to push it to towards the headgroup region as the fluid lamellar phase approached. The drug interactions with cholesterol during the mixed [lo + ld] phases indicate that these compounds may be partitioning into the liquid-ordered phase under these conditions. Use of an Enzyme Substrate to Investigate Bilayer Dynamics – DROSS NMR, 31P NMR and fluorescence emission spectroscopy were used to analyse the effect of catalysing an enzyme substrate on a lipid bilayer. 1,2-Dioctanoyl-sn-glycerol (DOG) is a substrate of DGK. DGK phosphorylates DGK in the presence of adenosine triphosphate (ATP), producing phosphatidic acid (PA). DROSS was used to generate order parameters while fluorescence emission spectroscopy was used to give an indication of bilayer tension. Bilayer tension and order parameters were lower for the sample containing PA co-dissolved with DOPC relative to the sample containing catalysed PA. This is due to sequestration of the catalysed PA in the immediate vicinity of the protein rather than an even distribution throughout the bilayer (as observed for co-dissolved PA), which affects the physical properties of the bilayer