Comment on "Surprises in threshold antikaon-nucleon physics"

It has recently been claimed by Oller et al. [PRL 95 (2005) 172502] that the DEAR kaonic hydrogen data can be reconciled with K^- p scattering data in a chiral unitary approach. In this comment we demonstrate that the proposed solution violates fundamental principles of scattering theory.Comment: 1 page, 1 figur

Thermodynamics and quark susceptibilities: a Monte-Carlo approach to the PNJL model

The Monte-Carlo method is applied to the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model. This leads beyond the saddle-point approximation in a mean-field calculation and introduces fluctuations around the mean fields. We study the impact of fluctuations on the thermodynamics of the model, both in the case of pure gauge theory and including two quark flavors. In the two-flavor case, we calculate the second-order Taylor expansion coefficients of the thermodynamic grand canonical partition function with respect to the quark chemical potential and present a comparison with extrapolations from lattice QCD. We show that the introduction of fluctuations produces only small changes in the behavior of the order parameters for chiral symmetry restoration and the deconfinement transition. On the other hand, we find that fluctuations are necessary in order to reproduce lattice data for the flavor non-diagonal quark susceptibilities. Of particular importance are pion fields, the contribution of which is strictly zero in the saddle point approximation

Wheel running as a function of varying effort requirements in rats

These experiments explore a wheel running work-response function with the goal of paralleling the drug magnitude-response (dose-response) function, as a way of measuring the value of running for rats. Friction levels were manipulated by varying the amount of weight applied to running wheels. Experiment 1 examined how male running patterns changed in response to weights applied on alternate days and calculated the work-response scores for each weight. Experiment 2 explored how male running changed when weights were applied for only a portion of the night, on an alternate night schedule. Experiments 3 and 4 replicated the procedures used in Experiments 1 and 2 with females. The results demonstrated that, whereas baseline running gradually decreased over days, it decreased further as the weights were increased for both males and females. However, the actual work expended running first increased then decreased as the weights increased. When the weights were applied and increased during the first few hours of the night, running decreased. After the weights were removed, male rats compensated by running more during the remaining friction-free hours of the night, however female rats did not show the same compensatory response pattern as the males. It is suggested that in males, the total distance traveled in the wheel rather than the total amount of work expended may more accurately represent what male rats regulate in their wheel running, which does not appear to be the case in females. It is suggested that the females\u27 estrous cycles may have confounded the results

Kaonic hydrogen and K^- p scattering

Chiral SU(3) effective field theory in combination with a relativistic coupled channels approach is used to perform a novel analysis of the strong interaction shift and width in kaonic hydrogen in view of the new accurate DEAR measurements. Questions of consistency with previous K^- p data are examined. Coulomb and isospin breaking effects turn out to be important and are both taken into account in this work.Comment: 4 pages, 4 figure

Meeting the challenges of micronutrient deficiencies in emergency-affected populations

Micronutrient deficiencies occur frequently in refugee and displaced populations. These deficiency diseases include, in addition to the most common Fe and vitamin A deficiencies, scurvy (vitamin C deficiency), pellagra (niacin and/or tryptophan deficiency) and beriberi (thiamin deficiency), which are not seen frequently in non-emergency-affected populations. The main causes of the outbreaks have been inadequate food rations given to populations dependent on food aid. There is no universal solution to the problem of micronutrient deficiencies, and not all interventions to prevent the deficiency diseases are feasible in every emergency setting. The preferred way of preventing these micronutrient deficiencies would be by securing dietary diversification through the provision of vegetables, fruit and pulses, which may not be a feasible strategy, especially in the initial phase of a relief operation. The one basic emergency strategy has been to include a fortified blended cereal in the ration of all food-aid-dependent populations (United Nations High Commissioner for Refugees/World Food Programme, 1997). In situations where the emergency-affected population has access to markets, recommendations have been to increase the general ration to encourage the sale and/or barter of a portion of the ration in exchange for locally-available fruit and vegetables (World Health Organization, 1999a, b, 2000). Promotion of home gardens as well as promotion of local trading are recommended longer-term options aiming at the self-sufficiency of emergency-affected households. The provision of fortified blended foods in the general ration has successfully prevented and controlled micronutrient deficiencies in various emergency settings. However, the strategy of relying only on fortified blended foods to prevent micronutrient deficiencies should be reviewed in the light of recurring evidence that provision of adequate supplies of these foods is often problematic. Donor policies on the bartering or exchange of food aid should also be clarified. Furthermore, the establishment of micronutrient surveillance systems, including standardized micronutrient deficiency diagnostic criteria, are vital for the control of micronutrient deficiency disease

Chiral Dynamics of Deeply Bound Pionic Atoms

We present and discuss a systematic calculation, based on two-loop chiral perturbation theory, of the pion-nuclear s-wave optical potential. A proper treatment of the explicit energy dependence of the off-shell pion self-energy together with (electromagnetic) gauge invariance of the Klein-Gordon equation turns out to be crucial. Accurate data for the binding energies and widths of the 1s and 2p levels in pionic ^{205}Pb and ^{207}Pb are well reproduced, and the notorious "missing repulsion" in the pion-nuclear s-wave optical potential is accounted for. The connection with the in-medium change of the pion decay constant is clarified.Comment: preprint ECT*-02-16, 4 pages, 3 figure

Possibility of s-wave pion condensates in neutron stars revisited

We examine possibilities of pion condensation with zero momentum (s-wave condensation) in neutron stars by using the pion-nucleus optical potential U and the relativistic mean field (RMF) models. We use low-density phenomenological optical potentials parameterized to fit deeply bound pionic atoms or pion-nucleus elastic scatterings. Proton fraction (Y_p) and electron chemical potential (mu_e) in neutron star matter are evaluated in RMF models. We find that the s-wave pion condensation hardly takes place in neutron stars and especially has no chance if hyperons appear in neutron star matter and/or b_1 parameter in U has density dependence.Comment: 4 pages, 3 figures, REVTe

Dispersion in a relativistic degenerate electron gas

Relativistic effects on dispersion in a degenerate electron gas are discussed by comparing known response functions derived relativistically (by Jancovici) and nonrelativistically (by Lindhard). The main distinguishing feature is one-photon pair creation, which leads to logarithmic singularities in the response functions. Dispersion curves for longitudinal waves have a similar tongue-like appearance in the relativistic and nonrelativistic case, with the main relativistic effects being on the Fermi speed and the cutoff frequency. For transverse waves the nonrelativistic treatment has a nonphysical feature near the cutoff frequency for large Fermi momenta, and this is attributed to an incorrect treatment of the electron spin. We find (with two important provisos) that one-photon pair creation is allowed in superdense plasmas, implying relatively strong coupling between transverse waves and pair creation.Comment: 17 pages, 9 figures. Submitted to Physical Review

Relativistic quantum plasma dispersion functions

Relativistic quantum plasma dispersion functions are defined and the longitudinal and transverse response functions for an electron (plus positron) gas are written in terms of them. The dispersion is separated into Landau-damping, pair-creation and dissipationless regimes. Explicit forms are given for the RQPDFs in the cases of a completely degenerate distribution and a nondegenerate thermal (J\"uttner) distribution. Particular emphasis is placed on the relation between dissipation and dispersion, with the dissipation treated in terms of the imaginary parts of RQPDFs. Comparing the dissipation calculated in this way with the existing treatments leads to the identification of errors in the literature, which we correct. We also comment on a controversy as to whether the dispersion curves in a superdense plasma pass through the region where pair creation is allowed.Comment: 16 pages, 1 figur