Atmospheric Polycyclic Aromatic Hydrocarbons: An Aspect of Air Pollution in Fairbanks, Alaska

Quantitative analysis of atmospheric polycyclic aromatic hydrocarbons (PAH) in Fairbanks, Alaska revealed significant levels of representative components. A fairly constant PAH pattern was observed throughout the winter of 1976-77, and the absolute PAH level correlated with air stagnation. Consideration of relative levels of individual PAH components reveals vehicular emissions as the major source but also provides evidence for contributions from power plant emissions. Fairbanks' PAH levels approach those of major cities in more moderate climates, and this situation emphasizes the importance of air quality problems in development of the Arctic

Probing empirical contact networks by simulation of spreading dynamics

Disease, opinions, ideas, gossip, etc. all spread on social networks. How these networks are connected (the network structure) influences the dynamics of the spreading processes. By investigating these relationships one gains understanding both of the spreading itself and the structure and function of the contact network. In this chapter, we will summarize the recent literature using simulation of spreading processes on top of empirical contact data. We will mostly focus on disease simulations on temporal proximity networks -- networks recording who is close to whom, at what time -- but also cover other types of networks and spreading processes. We analyze 29 empirical networks to illustrate the methods

Constraints on the richness–mass relation and the optical-SZE positional offset distribution for SZE-selected clusters

We cross-match galaxy cluster candidates selected via their Sunyaev-Zel'dovich effect (SZE) signatures in 129.1 deg$^2$ of the South Pole Telescope 2500d SPT-SZ survey with optically identified clusters selected from the Dark Energy Survey (DES) science verification data. We identify 25 clusters between $0.1\lesssim z\lesssim 0.8$ in the union of the SPT-SZ and redMaPPer (RM) samples. RM is an optical cluster finding algorithm that also returns a richness estimate for each cluster. We model the richness $\lambda$-mass relation with the following function $\langle\ln\lambda|M_{500}\rangle\propto B_\lambda\ln M_{500}+C_\lambda\ln E(z)$ and use SPT-SZ cluster masses and RM richnesses $\lambda$ to constrain the parameters. We find $B_\lambda= 1.14^{+0.21}_{-0.18}$ and $C_\lambda=0.73^{+0.77}_{-0.75}$. The associated scatter in mass at fixed richness is $\sigma_{\ln M|\lambda} = 0.18^{+0.08}_{-0.05}$ at a characteristic richness $\lambda=70$. We demonstrate that our model provides an adequate description of the matched sample, showing that the fraction of SPT-SZ selected clusters with RM counterparts is consistent with expectations and that the fraction of RM selected clusters with SPT-SZ counterparts is in mild tension with expectation. We model the optical-SZE cluster positional offset distribution with the sum of two Gaussians, showing that it is consistent with a dominant, centrally peaked population and a sub-dominant population characterized by larger offsets. We also cross-match the RM catalog with SPT-SZ candidates below the official catalog threshold significance $\xi=4.5$, using the RM catalog to provide optical confirmation and redshifts for additional low-$\xi$ SPT-SZ candidates.In this way, we identify 15 additional clusters with $\xi\in [4,4.5]$ over the redshift regime explored by RM in the overlapping region between DES science verification data and the SPT-SZ survey.Comment: 15 pages, 8 Figures, submitted to MNRA

The Chemistry of Plant/Animal Interactions

Chemical approaches to studying plant/animal interactions have led to an appreciation that plant chemistry strongly influences patterns of herbivory. Although this chemistry is often rather complex, two basic factors have emerged: plant chemistry influences herbivores in both positive and negative ways by determining dietary quality of plants and by providing feeding cues. Examination of the results from numerous studies addressing these issues has led to the development of three working hypotheses: (1) there is a molecular basis for chemical cues; (2) the molecular diversity of chemical signals implies specific mechanisms for plant-initiated attraction or repellence of herbivores; and (3) there are dynamic elements to many plant chemical defense

Condensed Tannins in Plant Defense: A Perspective on Classical Theories

Classical theories of condensed tannin-herbivore interactions should be reassesed. Condensed tannins may act in ways apart from digestion inhibition and may even act as metabolic toxins outside of the digestive system. Recent research has also questioned the generalized nature of condensed tannins as plant defenses; some condensed tannins are more deleterious to herbivores than others. In cases where condensed tannins do act as defensive compounds, however, animals may learn through experience rather than instinctively avoid high tannin content plants