Sigma and omega meson propagation in a dense nuclear medium

The propagation of the scalar ($\sigma$) and vector ($\omega$) mesons in nuclear matter is studied in detail using the Walecka model over a wide range of densities and including the effects of a finite $\sigma$ width through the inclusion of a two-pion loop. We calculate the dispersion relation and spectral functions of the $\sigma$ and (transverse and longitudinal) $\omega$ mesons, including the effect of $\sigma$-$\omega$ mixing in matter. It is shown that the mixing effect is quite important in the propagation of the (longitudinal) $\omega$ and $\sigma$ mesons above normal nuclear matter density. We find that there is a two-peak structure in the spectral function of the $\sigma$ channel, caused by $\sigma$-$\omega$ mixing.Comment: 17 pages including 6 ps files, submitted to Phys. Lett. B. Acknowledgement is revise

Revisiting chaos in stimulus-driven spiking networks: signal encoding and discrimination

Highly connected recurrent neural networks often produce chaotic dynamics, meaning their precise activity is sensitive to small perturbations. What are the consequences for how such networks encode streams of temporal stimuli? On the one hand, chaos is a strong source of randomness, suggesting that small changes in stimuli will be obscured by intrinsically generated variability. On the other hand, recent work shows that the type of chaos that occurs in spiking networks can have a surprisingly low-dimensional structure, suggesting that there may be "room" for fine stimulus features to be precisely resolved. Here we show that strongly chaotic networks produce patterned spikes that reliably encode time-dependent stimuli: using a decoder sensitive to spike times on timescales of 10's of ms, one can easily distinguish responses to very similar inputs. Moreover, recurrence serves to distribute signals throughout chaotic networks so that small groups of cells can encode substantial information about signals arriving elsewhere. A conclusion is that the presence of strong chaos in recurrent networks does not prohibit precise stimulus encoding.Comment: 8 figure

Calendar of Events News and Notes On the Web

Certain U.S. drinking water regulations have the potential to conflict with each other. This means that small system operators cannot simply comply with these mandates individually, but must consider how changing their treatment process to meet one rule might affect compliance with other rules. This Tech Brief provides information and strategies to effectively comply with those regulations that are most likely to conflict with one another

The RD Parent Empowerment Program Creates Measurable Change in the Behaviors of Low-Income Families and Children: An Intervention Description and Evaluation

Dietary and physical activity habits are developed early in life and are influenced by family environments. We describe and evaluate an intervention for low-income families to encourage healthy habits. The RD Parent Empowerment Program (http://www.eatright.org/programs/kidseatright/activities/content.aspx?id=6442477891) consists of four workshops centered on the 8 Habits of Healthy Children and Families (Academy of Nutrition and Dietetics Foundation). Registered dietitian nutritionists conduct the workshops in school and community settings using a structured leader guide and tailor the communication and interactive activities to the audience. Participants are parents of young children. Our goals were to use a phenomenologic approach to elicit participant feedback, determine whether participants in the RD Parent Empowerment Program made healthier choices for their families after attending the workshops, and identify which elements of the program participants believed contributed most to its success. The evaluation design used a pragmatic, mixed-methods approach utilizing postintervention focus groups and pre–post-intervention scores on the Family Nutrition and Physical Activity (FNPA) survey. All workshop attendees aged 18 years or older were eligible to participate in the evaluation. One hundred twenty-three parents participated in the intervention across seven sites. Focus group results were analyzed using thematic analysis methods to match themes to the main intervention goals. t-Tests were used to compare pre-and post-intervention FNPA scores and demographic characteristics pooled across sites. FNPA scores significantly improved from pre- to postintervention by a mean of 4.3 FNPA points (6.5%; P\u3c0.01). Focus group participants reported behavior changes as a result of the program and identified the site leaders as integral to the program’s success, triangulating the results. The RD Parent Empowerment Program generates meaningful self-reported behavior change in parents. The long-term sustainability of the changes must be investigated

Modified Quark-Meson Coupling Model for Nuclear Matter

The quark-meson coupling model for nuclear matter, which describes nuclear matter as non-overlapping MIT bags bound by the self-consistent exchange of scalar and vector mesons, is modified by introducing medium modification of the bag constant. We model the density dependence of the bag constant in two different ways: one invokes a direct coupling of the bag constant to the scalar meson field, and the other relates the bag constant to the in-medium nucleon mass. Both models feature a decreasing bag constant with increasing density. We find that when the bag constant is significantly reduced in nuclear medium with respect to its free-space value, large canceling isoscalar Lorentz scalar and vector potentials for the nucleon in nuclear matter emerge naturally. Such potentials are comparable to those suggested by relativistic nuclear phenomenology and finite-density QCD sum rules. This suggests that the reduction of bag constant in nuclear medium may play an important role in low- and medium-energy nuclear physics.Comment: Part of the text is reordered, revised version to appear in Phys. Rev. C. 19 pages, ReVTeX, 4 figures embedde

The RD Parent Empowerment Program Creates Measurable Change in the Behaviors of Low-Income Families and Children: An Intervention Description and Evaluation

Dietary and physical activity habits are developed early in life and are influenced by family environments. We describe and evaluate an intervention for low-income families to encourage healthy habits. The RD Parent Empowerment Program (http://www.eatright.org/programs/kidseatright/activities/content.aspx?id=6442477891) consists of four workshops centered on the 8 Habits of Healthy Children and Families (Academy of Nutrition and Dietetics Foundation). Registered dietitian nutritionists conduct the workshops in school and community settings using a structured leader guide and tailor the communication and interactive activities to the audience. Participants are parents of young children. Our goals were to use a phenomenologic approach to elicit participant feedback, determine whether participants in the RD Parent Empowerment Program made healthier choices for their families after attending the workshops, and identify which elements of the program participants believed contributed most to its success. The evaluation design used a pragmatic, mixed-methods approach utilizing postintervention focus groups and pre–post-intervention scores on the Family Nutrition and Physical Activity (FNPA) survey. All workshop attendees aged 18 years or older were eligible to participate in the evaluation. One hundred twenty-three parents participated in the intervention across seven sites. Focus group results were analyzed using thematic analysis methods to match themes to the main intervention goals. t-Tests were used to compare pre- and postintervention FNPA scores and demographic characteristics pooled across sites. FNPA scores significantly improved from pre- to postintervention by a mean of 4.3 FNPA points (6.5%; P\u3c0.01). Focus group participants reported behavior changes as a result of the program and identified the site leaders as integral to the program’s success, triangulating the results. The RD Parent Empowerment Program generates meaningful self-reported behavior change in parents. The long-term sustainability of the changes must be investigated

Photons from Hadronic Matter at Finite Temperature

Temperature dependence of hadronic decay widths and masses are studied within the framework of an effective Lagrangian approach. At finite temperature the hadronic masses do not seem to follow a universal scaling law. Considering an exhaustive set of hadronic reactions and vector meson decays we have estimated the photon spectrum emitted from hot hadronic matter taking into account medium effects through thermal loop corrections on the hadronic decay widths and masses. An enhancement in photon emission rate is obtained when we use the in-medium masses of vector mesons in our calculations. It is observed that the effect of $\rho$ decay width on the photon spectra is negligible.Comment: changed content, added references and figures.(30 pages, Figures included). To appear in Nuclear Physics

Roughness of Interfacial Crack Front: Correlated Percolation in the Damage Zone

We show that the roughness exponent zeta of an in-plane crack front slowly propagating along a heterogeneous interface embeded in a elastic body, is in full agreement with a correlated percolation problem in a linear gradient. We obtain zeta=nu/(1+nu) where nu is the correlation length critical exponent. We develop an elastic brittle model based on both the 3D Green function in an elastic half-space and a discrete interface of brittle fibers and find numerically that nu=1.5, We conjecture it to be 3/2. This yields zeta=3/5. We also obtain by direct numerical simulations zeta=0.6 in excellent agreement with our prediction. This modelling is for the first time in close agreement with experimental observations.Comment: 4 pages RevTeX