Stigmatomma (Fulakora) zwaluwenburgi, a New Species of Ponerine Ant from Hawaii

xBio:D Automated Uploa

Super-alimentation of gilts during lactation

Sows attempt to meet the sudden and large metabolic demand of lactation by increasing their level of voluntary food intake. However, the voluntary food intake of most sows during lactation generally does not provide sufficient energy or protein to meet their requirements for maintenance and milk production. By providing multiparous sows with extra food during lactation (via a gastric cannula) they remained in an anabolic state, and both milk production and piglet growth were increased (Matzat et al., 1990). Do gilts respond in the same way as sows to extra food in lactation? Gilts are smaller than sows and would be expected to have a greater impetus for body growth because they have not reached their mature body size. If gilts are provided with extra food during lactation, they might partition more of it into body tissue and less into milk. Gilts, fitted with gastric cannulas, were used to test the hypothesis that they would respond differently from the sows of Matzat et al. (1990) to extra food in lactation

Baryon resonances from a novel fat-link fermion action

We present first results for masses of positive and negative parity excited baryons in lattice QCD using an O(a^2) improved gluon action and a Fat Link Irrelevant Clover (FLIC) fermion action in which only the irrelevant operators are constructed with fat links. The results are in agreement with earlier calculations of N^* resonances using improved actions and exhibit a clear mass splitting between the nucleon and its chiral partner, even for the Wilson fermion action. The results also indicate a splitting between the lowest J^P = 1/2^- states for the two standard nucleon interpolating fields.Comment: 5 pages, 3 figures, talk given by W.Melnitchouk at LHP 2001 workshop, Cairns, Australi

Kaon Electromagnetic Production on Nuclei

The formation and excitation of hypernuclei through kaon photoproduction is reviewed. Basic features of the production process are emphasized. The possibility of extracting new information on hypernuclear structure and on the wave function of the bound $\Lambda$ is discussed. New results are presented for the quasifree production process $A(\gamma, K \Lambda)B$. Observables of this reaction are shown to be sensitive to the $\Lambda$-nucleus final state interaction.Comment: 10 pages, 4 figures. Invited talk given at the International Conference on Hypernuclear and Strange Particle Physics (HYP97), Brookhaven National Laboratory, USA, October 13-18, 1997. To be published in Nucl. Phys.

Spin-3/2 Nucleon and Delta Baryons in Lattice QCD

We present first results for masses of spin-3/2 N and Delta baryons in lattice QCD using Fat-Link Irrelevant Clover (FLIC) fermions. Spin-3/2 interpolating fields providing overlap with both spin-3/2 and spin-1/2 states are considered. In the isospin-1/2 sector, we observe, after appropriate spin and parity projection, a strong signal for the J^P=3/2^- state together with a weak but discernible signal for the 3/2^+ state with a mass splitting near that observed experimentally. We also find good agreement between the 1/2^+/- masses and earlier nucleon mass simulations with the standard spin-1/2 interpolating field. For the isospin-3/2 Delta states, clear mass splittings are observed between the various 1/2^+/- and 3/2^+/- channels, with the calculated level orderings in good agreement with those observed empirically.Comment: 17 pages, 8 figures, 2 table

Infrared Behavior of the Gluon Propagator on a Large Volume Lattice

The first calculation of the gluon propagator using an order a^2 improved action with the corresponding order a^2 improved Landau gauge fixing condition is presented. The gluon propagator obtained from the improved action and improved Landau gauge condition is compared with earlier unimproved results on similar physical lattice volumes of 3.2^3 \times 6.4 fm^4. We find agreement between the improved propagator calculated on a coarse lattice with lattice spacing a = 0.35 fm and the unimproved propagator calculated on a fine lattice with spacing a = 0.10 fm. This motivates us to calculate the gluon propagator on a coarse large-volume lattice 5.6^3 \times 11.2 fm^4. The infrared behavior of previous studies is confirmed in this work. The gluon propagator is enhanced at intermediate momenta and suppressed at infrared momenta. Therefore the observed infrared suppression of the Landau gauge gluon propagator is not a finite volume effect.Comment: 8 pages, 4 figures, minor typos corrected and repsonse to referees comment

Novel fat-link fermion actions

The hadron mass spectrum is calculated in lattice QCD using a novel fat-link clover fermion action in which only the irrelevant operators of the fermion action are constructed using smeared links. The simulations are performed on a 16^3 X 32 lattice with a lattice spacing of a=0.125 fm. We compare actions with n=4 and 12 smearing sweeps with a smearing fraction of 0.7. The n=4 Fat Link Irrelevant Clover (FLIC) action provides scaling which is superior to mean-field improvement, and offers advantages over nonperturbative O(a) improvement.Comment: 5 pages, 2 figures, talk given by J.Zanotti at LHP 2001 workshop, Cairns, Australi

Quasifree kaon-photoproduction from nuclei in a relativistic approach

We compute the recoil polarization of the lambda-hyperon and the photon asymmetry for the quasifree photoproduction of kaons in a relativistic impulse-approximation approach. Our motivation for studying polarization observables is threefold. First, polarization observables are more effective discriminators of subtle dynamics than the unpolarized cross section. Second, earlier nonrelativistic calculations suggest an almost complete insensitivity of polarization observables to distortions effects. Finally, this insensitivity entails an enormous simplification in the theoretical treatment. Indeed, by introducing the notion of a ``bound-nucleon propagator'' we exploit Feynman's trace techniques to develop closed-form, analytic expressions for all photoproduction observables. Moreover, our results indicate that polarization observables are also insensitive to relativistic effects and to the nuclear target. Yet, they are sensitive to the model parameters, making them ideal tools for the study of modifications to the elementary amplitude --- such as in the production, propagation, and decay of nucleon resonances --- in the nuclear medium.Comment: 15 pages and 6 figures - submitted to PR