Crystal data for some sodium rare earth silicates

Single crystal synthesis, X-ray powder diffraction data, and electron microprobe data are given for some Na rare earth silicates of the types NaMSiO₄, Na₃MSi₂O₇, Na₃MSi₃O₉, and Na₅MSi₄O₁₂. NaYSiO₄ is orthorhombic with SG Pbn2₁, a=5.132, b=11.156, anc c=6.405 Å. NaGdSiO₄ is tetragonal with SG I4 or I \(\bar 4\) with a=11.743 and c=5.444 Å. A second form of NaGdSiO₄ is orthorhombic with SG P2₁ nb or Pmmb, a=9.179, b=27.29, and c=5.472 Å. Na₃YSi₂O₇ is hexagonal with a=9.416 and c=13.776 Å. Na₃YSi₃O₉ is orthorhombic with a=15.215, b=15.126, and c=15.036 Å. Na ion conductivities of Na₃YSi₂O₇ and Na₃YSi₃O₉ at 300° C of 5×10^?6 (Θ-cm)^?1 and 6×10^?6 (Θ-cm)^?1, respectively, are substantially less than that for Na₆YSi₄O₁₂, 1×10^?1 (Θ-cm)^?1.     

Metal tissue levels in Steller sea lion (Eumetopias jubatus) pups

The endangered Western population of the Steller sea lion declined for three decades for uncertain reasons. We present baseline data of metal concentrations in pups as a first step towards investigating the potential threat of developmental exposures to contaminants. Seven metals were investigated: arsenic, cadmium, silver, aluminum, mercury, lead and vanadium. Vanadium was detected in only a single blubber sample. Mercury appears to be the most toxicologically significant metal with concentrations in the liver well above the current action level for mercury in fish. The concentrations of aluminum, arsenic, silver, cadmium and lead were present in one-fourth to two-thirds of all samples and were at either comparable or below concentrations previously reported. Neither gender nor region had a significant effect on metal burdens. Future work should consider metal concentrations in juveniles and adults and toxicological studies need to be performed to begin to assess the toxicity of these metals.     

What is the relationship between food shopping and daily mobility? A relational approach to analysis of food access

Recent research on food access has increasingly focused on how individuals’ daily mobility, much of it based on activity spaces created from GPS data. In this paper, we expand this research through an analysis of a large transit survey (n = 21,298 households) from Minneapolis/St. Paul, Minnesota. We do this using relational approach focused on the topological connections found in household travel patterns rather than measures of exposure based on geographic distance. Our exploratory data analysis analyzes both grocery shopping and eating out across the metropolitan area, focusing on the position of utilized food sources relative to home and work locations, utilized modes of transit, and other daily activities often combined with food shopping. Households often used food sources located outside their residential neighborhoods, usually moving toward the central city to do so. Eating out occurred farther from home than grocery shopping, though in many cases close to work. Automobile use was most common for grocery shopping trips, but less so in the lowest income households and in the central city. Our findings show that a relational approach can identify distinctive patterns in everyday food provisioning by emphasizing the connections between food shopping and other everyday household activities.     

Silicon Deficiency Induces Alkaline Phosphatase Enzyme Activity in Cultures of Four Marine Diatoms

Alkaline phosphatase (AP) was detected using ELF-97® in silicon-starved Pseudo-nitzschia multiseries cells; thus, we tested two, alternative hypotheses: Pseudo-nitzschia multiseries has a high phosphate demand, showing signs of phosphate deficiency even when concentrations of orthophosphate are high, or silicate deficiency can stimulate the AP enzyme in this species. We also studied the effect of silicon deficiency on AP in three other common marine diatoms: Thalassiosira pseudonana, Nitzschia pusilla, and Nitschia closterium. Each of the species tested showed a different pattern of AP regulation. AP levels, however, increased in the four diatoms as a result of silicon deficiency, suggesting that AP may be involved in a variety of intracellular processes related to silicon deficiency. Additionally, the results of this study indicate that AP could be stimulated by stressors other than phosphate deficiency, such as silicon deficiency; therefore, it should be used cautiously as an indicator of phosphate limitation.     

The role of FAST in pulsar timing arrays

The Five-hundred-meter Aperture Spherical radio Telescope(FAST) will become one of the world-leading telescopes for pulsar timing array(PTA) research. The primary goals for PTAs are to detect(and subsequently study) ultra-low-frequency gravitational waves, to develop a pulsar-based time standard and to improve solar system planetary ephemerides. FAST will have the sensitivity to observe known pulsars with significantly improved signal-to-noise ratios and will discover a large number of currently unknown pulsars. We describe how FAST will contribute to PTA research and show that jitter-and timing-noise will be the limiting noise processes for FAST data sets. Jitter noise will limit the timing precision achievable over data spans of a few years while timing noise will limit the precision achievable over many years.