ALBERT

Description: We reanalyze a data set of hydrocarbons in ambient air obtained by gas chromatography-mass spectrometry at a surface site in Pasadena in the Los Angeles basin during the NOAA California Nexus study (CalNex) in 2010. The number of hydrocarbon compounds quantified from the chromatograms is expanded through the use of new peak-fitting data analysis software. We also re-examine hydrocarbon removal processes. For alkanes, small alkenes and aromatics, the removal is determined by the reaction with hydroxyl (OH) radicals. For several highly reactive alkenes, the nighttime removal by ozone and nitrate (NO 3 ) radicals is also significant. We discuss how this nighttime removal affects the determination of emission ratios vs. carbon monoxide (CO) and show that previous estimates based on nighttime correlations with CO were too low. We analyze model output from the chemistry-transport model WRF-Chem for hydrocarbons and radicals at the Pasadena location to evaluate our methods for determining emission ratios from the measurements. We find that our methods agree with the modeled emission ratios for the domain centered on Pasadena, and that the modeled emission ratios vary by 23% across the wider South Coast basin. We compare the alkene emission ratios with published results from ambient measurements, and from tunnel and dynamometer studies of motor vehicle emissions. We find that with few exceptions the composition of alkene emissions determined from the measurements in Pasadena closely resembles that of motor vehicle emissions.

Description: We developed a new nitrogen oxides (NO x ) and carbon monoxide (CO) emission inventory for the Los Angeles-South Coast Air Basin (SoCAB) expanding the Fuel-based Inventory for motor-Vehicle Emissions (FIVE) and applied it in regional chemical transport modeling focused on the California Nexus of Air Quality and Climate Change (CalNex) 2010 field campaign. The weekday NO x emission over the SoCAB in 2010 is 620 metric tons day −1 while the weekend emission is 410 metric tons day −1 . The NO x emission decrease on weekends is caused by reduced diesel truck activities. Weekday and weekend CO emissions over this region are similar: 2340 and 2180 metric tons day −1 , respectively. Previous studies reported large discrepancies between the airborne observations of NO x and CO mixing ratios and the model simulations for CalNex based on the available bottom-up emission inventories. Utilizing the newly developed emission inventory in this study, the simulated NO x and CO mixing ratios agree with the observations from the airborne and the ground-based in-situ and remote-sensing instruments during the field study. The simulations also reproduce the weekly cycles of these chemical species. Both the observations and the model simulations indicate that decreased NO x on weekends leads to enhanced photochemistry and increase of O 3 and O x (=O 3  + NO 2 ) in the basin. The emission inventory developed in this study can be extended to different years and other urban regions in the US to study the long-term trends in O 3 and its precursors with regional chemical transport models.

Description: 〈span〉〈div〉Abstract〈/div〉The rare thiospinel siegenite (CoNi〈sub〉2〈/sub〉S〈sub〉4〈/sub〉) has been found in drill-core samples of quartz-norite as primary oriented intergrowths in millerite from the Morokweng impact site, South Africa. The mineral occurs as elongate, sub-parallel grains (10 × 50 μm on average, up to 100 × 500 μm) that are light purple under reflected light. Quantitative reflectance data compares well to current data sets and shows little variation among other Ni-Co thiospinel endmembers. The average major element chemistry of siegenite (〈span〉n〈/span〉 = 19) includes (wt.%): Fe 1.69 (0.65–2.99), Co 12.46 (7.92–15.72), Ni 43.84 (39.29–47.68), and S 41.90 (41.25–42.26), corresponding to the average formula (Co〈sub〉0.64〈/sub〉Ni〈sub〉0.28〈/sub〉Fe〈sub〉0.09〈/sub〉)〈sub〉Σ1.01〈/sub〉Ni〈sub〉2.00〈/sub〉S〈sub〉3.98〈/sub〉 (based on 7 atoms per formula unit). Laser-Raman spectroscopy along with single-crystal X-ray diffraction results supports the space group assignment, with no evidence to suggest a phase transformation. The X-ray diffraction data also support the inverse cation distribution for siegenite. Electron backscattered diffraction (EBSD) indicates that the siegenite (sgn) and millerite (mlr) are present in one of two possible crystallographic orientations (shared plane, orientation of plane): (1) (100)[012]〈sub〉mlr〈/sub〉||(111)[10]〈sub〉sgn〈/sub〉 or (2) (001)[10]〈sub〉mlr〈/sub〉||(110)[11]〈sub〉sgn〈/sub〉. Further examination with EBSD suggests that the siegenite is twinned on {111} forming simple lamellar twins. Based on the data presented, it is suggested that the sequence of crystallization was millerite → siegenite → chalcopyrite, initiated by nucleation of Ni〈sub〉1–〈/sub〉〈span〉x〈/span〉S (millerite, at high 〈span〉T〈/span〉) and followed by the formation of siegenite between 356 and 282 °C which crystallized alongside metal-deficient Ni〈sub〉1–〈/sub〉〈span〉x〈/span〉S. This process caused the co-crystallization of millerite and siegenite, forming the oriented crystal-controlled intergrowth observed in the Morokweng quartz-norite impact melt sheet. 〈/span〉

Description: Pyrrhotite (Po) from five orebodies (830, 865, 880, 890, and 100 OB) in the Copper Cliff Offset Dike (CCOD) at Sudbury, Ontario was studied using powder X-ray diffraction data and Rietveld analysis, SEM-EDS, magnetic colloid, optical petrographic techniques, and Laser Ablation-ICP-MS in order to: (1) quantify the distribution of NC (non-magnetic, symmetry higher than monoclinic) and 4C (magnetic, monoclinic in symmetry) Po; (2) characterize the major, minor, and trace-element chemistries of both polymorphs; and (3) determine the factors enhancing the stability of NC Po. Results confirm that both NC and 4C Po are present, with ratios varying between 0 to 0.97. In general, 4C Po is the dominant polymorph within the sampled OB, with the exception of the 100 OB, which is dominated by NC Po. Mineral chemistry indicates that there is an almost complete compositional overlap between the major, minor, and trace-element compositions of NC and 4C Po from the CCOD. The data also show that both polymorphs are slightly metal-deficient relative to the ideal chemistry of 4C Po, Fe 7 S 8 . There were no significant differences found in the Ni contents of either polymorph. Data revealed that the main mineralogical difference between the five OB was the presence of ilmenite in the 830, 865, 880, and 890 OB, whereas magnetite dominates in the 100 OB. Mineralization occurs along the eastern margin of the 830–890 OB, in contrast to the 100 OB, where mineralization occurs in the center of the dike. The increased abundance of NC Po in the 100 OB may be explained by this difference in the style of mineralization, specifically, the proximity of ore to the surrounding country rock. Therefore, f O 2 may have directly influenced the distribution and stabilization of NC Po, which would then impact the observed NC:4C Po ratios in the selected OB.

Description: We present data from a new mobile system intended to aid in the design of upcoming urban CO 2 monitoring networks. Our collected data include GPS probe data, video-derived traffic density, and accurate CO 2 concentration measurements. The method described here is economical, scalable, and self-contained, allowing for potential future deployment in locations without existing traffic infrastructure or vehicle fleet information. Using a test data set collected on California Highway 24 over a two-week period, we observe that on-road CO 2 concentrations are elevated by a factor of two in congestion compared to free-flow conditions. This result is found to be consistent with a model including vehicle induced turbulence and standard engine physics. In contrast to surface concentrations, surface emissions are found to be relatively insensitive to congestion. We next use our model for CO 2 concentration together with our data to independently derive vehicle emission rate parameters. Parameters scaling the leading four emission rate terms are found to be within 25% of those expected for a typical passenger car fleet, enabling us to derive instantaneous emission rates directly from our data that compare generally favorably to predictive models presented in the literature. The present results highlight the importance of high spatial and temporal resolution traffic data for interpreting on- and near-road concentration measurements. Future work will focus on transport and the integration of mobile platforms into existing stationary network designs.

Description: To monitor the pan-Arctic seasonal freeze-thaw transitions of the land surface and sea ice, we analyze daily backscatter data from satellite scatterometry to examine the time series on an annual basis by applying an optimal edge detection scheme, and iterate against an internal median climatology to mitigate unreasonable outliers. By applying this novel algorithm to resolution-enhanced QuikSCAT data from 1999 to 2009, we have mapped a decade of seasonal freeze-thaw transitions across the landmass and sea ice north of 60°N at a spatial resolution better than 5 km. The data set has been validated against surface air temperature measurements and snow depth obtained from a distributed network of weather stations and drift buoys. Most retrieved timings from surface and QuikSCAT measurements agree to less than a week at thaw transition for both land and sea ice and at freeze transition for sea ice, indicating successful retrieval over a range of surface covers. While the spatial pattern of freeze-thaw transition changes substantially from year to year, the interannual variability of the mean transition timing over a particular surface is small.

Description: Author(s): G. Moody, C. McDonald, A. Feldman, T. Harvey, R. P. Mirin, and K. L. Silverman Minimizing decoherence due to coupling of a quantum system to its fluctuating environment is at the forefront of quantum information and photonics research. Nature sets the ultimate limit, however, given by the strength of the system’s coupling to the electromagnetic field. Here, we establish the ab… [Phys. Rev. Lett. 116, 037402] Published Fri Jan 22, 2016

Description: Polycomb group (PcG) proteins are involved in epigenetic silencing where they function as major determinants of cell identity, stem cell pluripotency and the epigenetic gene silencing involved in cancer development. Recently numerous PcG proteins, including CBX4, have been shown to accumulate at sites of DNA damage. However, it remains unclear whether or not CBX4 or its E3 sumo ligase activity is directly involved in the DNA damage response (DDR). Here we define a novel role for CBX4 as an early DDR protein that mediates SUMO conjugation at sites of DNA lesions. DNA damage stimulates sumoylation of BMI1 by CBX4 at lysine 88, which is required for the accumulation of BMI1 at DNA damage sites. Moreover, we establish that CBX4 recruitment to the sites of laser micro-irradiation-induced DNA damage requires PARP activity but does not require H2AX, RNF8, BMI1 nor PI-3-related kinases. The importance of CBX4 in the DDR was confirmed by the depletion of CBX4, which resulted in decreased cellular resistance to ionizing radiation. Our results reveal a direct role for CBX4 in the DDR pathway.

Description: A detailed electron microprobe (EMP) and laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) study of zircon from six types of miaskitic and agpaitic alkaline pegmatite from the Larvik Plutonic Complex, Oslo rift valley, Norway, was undertaken to shed light on the pegmatite petrogenesis. Detailed rare earth element (REE) analyses indicate important differences between the zircon from each type of pegmatite. Primary zircon from miaskitic Stavern-, Tvedalen- and Stålaker-type pegmatites has a mean ΣREE = 704 ppm, is depleted in LREE and has a significant positive Ce anomaly (Ce/Ce* = 44–67) and negative Eu anomaly (Eu/Eu* = 0.15–0.18). Secondary Tvedalen-type zircon is REE-enriched (ΣREE = 5035 ppm), with a flatter REE pattern, Ce/Ce* = 0.97 and a Eu anomaly similar to primary Tvedalen-type zircon (Eu/Eu* = 0.21). Secondary zircon from agpaitic Langesundsfjord-type pegmatites display a distinctive flat REE pattern characterized by overall REE enrichment (ΣREE = 967), Ce/Ce* = 1.92, and a minor negative Eu anomaly (Eu/Eu* = 0.37). Zircon from agpaitic Bratthagen-type pegmatites occurs as both altered primary and secondary phases and is strongly enriched in REE relative to other zircon (ΣREE = 4178 and 8388, respectively). Primary Bratthagen-type zircon has a similar REE pattern to miaskitic zircon, with a steeper HREE profile and smaller Ce and Eu anomalies (Eu/Eu* = 0.73; Ce/Ce* = 6.22). Secondary Bratthagen-type zircon is strongly enriched in LREE compared to primary zircon, does not display a positive Ce anomaly and has Eu/Eu* = 0.56. The altered primary and secondary Bratthagen-type zircons have elevated Th/UN ratios, suggesting a different melt source for Bratthagen-type agpaitic pegmatites. Zircon from external pegmatites has trace-element signatures similar to Stavern-, Tvedalen- and Stålaker-type primary zircon with Ce/Ce* = 214 and Nb/Ta and Th/U ratios that are similar to those of secondary Langesundsfjord- and Bratthagen-type zircon. It is suggested that the parental melt of the external pegmatites is the same as the miaskitic pegmatites, but that it has undergone alteration by hydrothermal fluids derived from the host basalt, or by post-magmatic F-rich fluids which mobilize Nb and Th. On the basis of texture, morphology and geochemistry, two populations of zircon can be recognized: (1) primary zircon from miaskitic pegmatites; and (2) secondary zircon from post-magmatic, hydrothermal assemblages. The U–Th–Pb isotope analyses indicate that the secondary and altered zircon are depleted in 238U, and enriched in LREE. Interaction of a post-magmatic hydrothermal fluid with an externally derived meteoric fluid is suggested to have influenced the REE signatures, and in particular the Eu and Ce anomalies of the late-stage zircons.

Description: Environmental Science & Technology DOI: 10.1021/es204290s