Nonabelian dark matter: models and constraints

Numerous experimental anomalies hint at the existence of a dark matter (DM) multiplet chi_i with small mass splittings. We survey the simplest such models which arise from DM in the low representations of a new SU(2) gauge symmetry, whose gauge bosons have a small mass mu < 1 GeV. We identify preferred parameters M_chi ~ 1 TeV, mu ~ 100 MeV, alpha_g ~ 0.04 and the chi chi -> 4e annihilation channel, for explaining PAMELA, Fermi, and INTEGRAL/SPI lepton excesses, while remaining consistent with constraints from relic density, diffuse gamma rays and the CMB. This consistency is strengthened if DM annihilations occur mainly in subhalos, while excitations (relevant to the excited DM proposal to explain the 511 keV excess) occur in the galactic center (GC), due to higher velocity dispersions in the GC, induced by baryons. We derive new constraints and predictions which are generic to these models. Notably, decays of excited DM states chi' -> chi gamma arise at one loop and could provide a new signal for INTEGRAL/SPI; big bang nucleosynthesis (BBN) constraints on the density of dark SU(2) gauge bosons imply a lower bound on the mixing parameter epsilon between the SU(2) gauge bosons and photon. These considerations rule out the possibility of the gauge bosons that decay into e^+e^- being long-lived. We study in detail models of doublet, triplet and quintuplet DM, showing that both normal and inverted mass hierarchies can occur, with mass splittings that can be parametrically smaller, e.g., O(100) keV, than the generic MeV scale of splittings. A systematic treatment of Z_2 symmetry which insures the stability of the intermediate DM state is given for cases with inverted mass hierarchy, of interest for boosting the 511 keV signal from the excited dark matter mechanism.Comment: 28 pages, 17 figures; v2. added brief comment, reference

Probing the equation of state of neutron-rich matter with intermediate energy heavy-ion collisions

Nuclear reactions induced by stable and/or radioactive neutron-rich nuclei provide the opportunity to pin down the equation of state of neutron-rich matter, especially the density ($\rho$) dependence of its isospin-dependent part, i.e., the nuclear symmetry energy $E_{\rm sym}$. A conservative constraint, $32(\rho /\rho_{0})^{0.7} < E_{\rm sym}(\rho ) < 32(\rho /\rho _{0})^{1.1}$, around the nuclear matter saturation density $\rho_0$ has recently been obtained from the isospin diffusion data in intermediate energy heavy-ion collisions. We review this exciting result and discuss its consequences and implications on nuclear effective interactions, radii and cooling mechanisms of neutron stars.Comment: 10 pages. Invited talks at (1) International Workshop on Nuclear Multifragmentation, Nov. 28-Dec. 1, 2005, Catania, Italy and (2) XXIX Symposium on Nuclear Physics, Jan. 3-6, 2006, Cocoyoc, Morelos, Mexic

Exposure to the Dental Environment and Prevalence of Respiratory Illness in Dental Student Populations

Objective: To determine if the prevalence of respiratory disease among dental students and dental residents varies with their exposure to the clinical dental environment. Methods: A detailed questionnaire was administered to 817 students at 3 dental schools. The questionnaire sought information concerning demographic characteristics, school year, exposure to the dental environment and dental procedures, and history of respiratory disease. The data obtained were subjected to bivariate and multiple logistic regression analysis. Results: Respondents reported experiencing the following respiratory conditions during the previous year: asthma (26 cases), bronchitis (11 cases), chronic lung disease (6 cases), pneumonia (5 cases) and streptococcal pharyngitis (50 cases). Bivariate statistical analyses indicated no significant associations between the prevalence of any of the respiratory conditions and year in dental school, except for asthma, for which there was a significantly higher prevalence at 1 school compared to the other 2 schools. When all cases of respiratory disease were combined as a composite variable and subjected to multivariate logistic regression analysis controlling for age, sex, race, dental school, smoking history and alcohol consumption, no statistically significant association was observed between respiratory condition and year in dental school or exposure to the dental environment as a dental patient. Conclusion: No association was found between the prevalence of respiratory disease and a student\u27s year in dental school or previous exposure to the dental environment as a patient. These results suggest that exposure to the dental environment does not increase the risk for respiratory infection in healthy dental health care workers

Bread and Circuses: Sports and Public Opinion in China

Sports victory constitutes an important part of propaganda in authoritarian states. The heavy state investment in sports industries and sports culture in China illustrates the political importance of sports. However, few studies have systematically examined the exact impact of sports propaganda on public opinion. Using a survey experiment conducted in two Chinese cities, this article finds that broadcast highlighting national sports achievements has significant positive effects on general satisfaction and compliance with the local governments. These results expand on the small but growing literature on the effects of sports on political opinions and help detail the specific ways in which sports can affect political attitudes

Multiple sclerosis presenting with homonymous hemianopia

Ophthalmic manifestations are a prominent feature of multiple sclerosis (MS). Optic neuritis accounts for 18% of initial MS symptoms and 40–70% of all patients with MS have at least one episode of optic neuritis during their disease course. Eye movement abnormalities such as internuclear ophthalmoplegia are seen in over 50% of patients with MS. This case study describes a rare initial presentation of MS with ‘left eye blurred vision’ and examination findings of a complete left homonymous hemianopia. Although homonymous hemianopia is uncommon (0.5–3.5% of MS cases), this case highlights an important reminder that people with a field defect often complain of ‘blurred vision’ on the side of the defect

Contributions of individual variation in temperature, solar radiation and precipitation to crop yield in the North China Plain, 1961–2003

An understanding of the relative impacts of the changes in climate variables on crop yield can help develop effective adaptation strategies to cope with climate change. This study was conducted to investigate the effects of the interannual variability and trends in temperature, solar radiation and precipitation during 1961–2003 on wheat and maize yields in a double cropping system at Beijing and Zhengzhou in the North China Plain (NCP), and to examine the relative contributions of each climate variable in isolation. 129 climate scenarios consisting of all the combinations of these climate variables were constructed. Each scenario contained 43 years of observed values of one variable, combined with values of the other two variables from each individual year repeated 43 times. The Agricultural Production Systems Simulator (APSIM) was used to simulate crop yields using the ensemble of generated climate scenarios. The results showed that the warming trend during the study period did not have significant impact on wheat yield potential at both sites, and only had significant negative impact on maize yield potential at Beijing. This is in contrast with previous results on effect of warming. The decreasing trend in solar radiation had a much greater impact on simulated yields of both wheat and maize crops, causing a significant reduction in potential yield of wheat and maize at Beijing. Although decreasing trends in rainfed yield of both simulated wheat and maize were found, the substantial interannual variability of precipitation made the trends less prominent

Phonon anharmonicity and negative thermal expansion in SnSe

The anharmonic phonon properties of SnSe in the Pnma phase were investigated with a combination of experiments and first-principles simulations. Using inelastic neutron scattering (INS) and nuclear resonant inelastic X-ray scattering (NRIXS), we have measured the phonon dispersions and density of states (DOS) and their temperature dependence, which revealed a strong, inhomogeneous shift and broadening of the spectrum on warming. First-principles simulations were performed to rationalize these measurements, and to explain the previously reported anisotropic thermal expansion, in particular the negative thermal expansion within the Sn-Se bilayers. Including the anisotropic strain dependence of the phonon free energy, in addition to the electronic ground state energy, is essential to reproduce the negative thermal expansion. From the phonon DOS obtained with INS and additional calorimetry measurements, we quantify the harmonic, dilational, and anharmonic components of the phonon entropy, heat capacity, and free energy. The origin of the anharmonic phonon thermodynamics is linked to the electronic structure.Comment: 14 pages, 12 figure

Olfactory learning alters navigation strategies and behavioral variability in C. elegans

Animals adjust their behavioral response to sensory input adaptively depending on past experiences. The flexible brain computation is crucial for survival and is of great interest in neuroscience. The nematode C. elegans modulates its navigation behavior depending on the association of odor butanone with food (appetitive training) or starvation (aversive training), and will then climb up the butanone gradient or ignore it, respectively. However, the exact change in navigation strategy in response to learning is still unknown. Here we study the learned odor navigation in worms by combining precise experimental measurement and a novel descriptive model of navigation. Our model consists of two known navigation strategies in worms: biased random walk and weathervaning. We infer weights on these strategies by applying the model to worm navigation trajectories and the exact odor concentration it experiences. Compared to naive worms, appetitive trained worms up-regulate the biased random walk strategy, and aversive trained worms down-regulate the weathervaning strategy. The statistical model provides prediction with $>90 \%$ accuracy of the past training condition given navigation data, which outperforms the classical chemotaxis metric. We find that the behavioral variability is altered by learning, such that worms are less variable after training compared to naive ones. The model further predicts the learning-dependent response and variability under optogenetic perturbation of the olfactory neuron AWC$^\mathrm{ON}$. Lastly, we investigate neural circuits downstream from AWC$^\mathrm{ON}$ that are differentially recruited for learned odor-guided navigation. Together, we provide a new paradigm to quantify flexible navigation algorithms and pinpoint the underlying neural substrates