A split-beam probe-pump-probe scheme for femtosecond time resolved protein X-ray crystallography

In order to exploit the femtosecond pulse duration of X-ray Free-Electron Lasers (XFEL) operating in the hard X-ray regime for ultrafast time-resolved protein crystallography experiments, critical parameters that determine the crystallographic signal-to-noise (I/σI) must be addressed. For single-crystal studies under low absorbed dose conditions, it has been shown that the intrinsic pulse intensity stability as well as mode structure and jitter of this structure, significantly affect the crystallographic signal-to-noise. Here, geometrical parameters are theoretically explored for a three-beam scheme: X-ray probe, optical pump, X-ray probe (or “probe-pump-probe”) which will allow experimental determination of the photo-induced structure factor amplitude differences, ΔF, in a ratiometric manner, thereby internally referencing the intensity noise of the XFEL source. In addition to a non-collinear split-beam geometry which separates un-pumped and pumped diffraction patterns on an area detector, applying an additional convergence angle to both beams by focusing leads to integration over mosaic blocks in the case of well-ordered stationary protein crystals. Ray-tracing X-ray diffraction simulations are performed for an example using photoactive yellow protein crystals in order to explore the geometrical design parameters which would be needed. The specifications for an X-ray split and delay instrument that implements both an offset angle and focused beams are discussed, for implementation of a probe-pump-probe scheme at the European XFEL. We discuss possible extension of single crystal studies to serial femtosecond crystallography, particularly in view of the expected X-ray damage and ablation due to the first probe pulse

Degeneracies between Modified Gravity and Baryonic Physics

In order to determine the observable signatures of modified gravity theories, it is important to consider the effect of baryonic physics. We use a modified version of the ISIS code to run cosmological hydrodynamic simulations to study degeneracies between modified gravity and radiative hydrodynamical processes. Of these, one was the standard $\Lambda$CDM model and four were variations of the Symmetron model. For each model we ran three variations of baryonic processes: non-radiative hydrodynamics; cooling and star formation; and cooling, star formation, and supernova feedback. We construct stacked gas density, temperature, and dark matter density profiles of the halos in the simulations, and study the differences between them. We find that both radiative variations of the models show degeneracies between their processes and at least two of the three parameters defining the Symmetron model.Comment: 9 pages, 4 figures, matches version accepted to A&

Furniture Stability: A Review of Data and Testing Results

This report by Kids In Danger (KID) and Shane's Foundation focuses on tip-overs of dressers and chests. ASTM International, which has developed thousands of voluntary industry consensus technical standards, has a standard in place to test furniture stability. However, furniture on the market is not required to conform, resulting in widespread non-compliance. Additionally, these standards are too lenient and require reform, as testing protocols have remained virtually unchanged for over a decade, despite continuing injuries and deaths. Units may pass the standard, but still present a significant risk. KID advocates for a two-pronged approach to decreasing tip-over incidents:Increasing consumer awareness of the danger of furniture tip-overs and knowledge of the actions needed to keep children safe, andImproving furniture stability by strengthening standards, making those standards mandatory and enforceable and promoting changes in furniture design.KID compiled data from incidents reported to the U.S. Consumer Product Safety Commission (CPSC) by various sources and from the National Electronic Injury Surveillance System (NEISS). These include reports from January 1, 2010 to October 14, 2015. Findings of the data analysis include:Two-year-olds are the age group most affected by tip-overs, especially in regard to fatal incidents.Children age 2 to 5 accounted for 77% of total incidents.The age range of children injured is wider than the age range of children killed by tip-overs.Fatalities accounted for 12% of total incidents.Head injuries (37%) were the most common category of injury.Almost all (98.7%) of head injuries are related to a television tipping over on a child.KID conducted performance tests on a sample of 19 dressers and chests. Testing was run at the UL Furniture Center of Excellence in Holland, Michigan. UL laboratory technicians followed a testing protocol developed by KID. The protocol included tests based on the current voluntary standard for furniture stability. KID added tests that, among other things, evaluated for tip-overs when more weight was added (simulating larger children), drawers were full of clothes, furniture was placed on carpeting as opposed to bare flooring, televisions were placed on top of the furniture, and additional drawers were opened simultaneous with weighting one drawer. These additional tests were intended to be more representative of real-world scenarios.Test results include:Only nine of the 19 units passed performance tests based on the current tip-over safety standard, ASTM F2057.Only two units passed all tests, including the additional testing protocols added by KID.The weight of a television or any type placed on top of the unit did not decrease the stability of furniture.Furniture placed on carpet is less stable than furniture placed on hard floors.Many units remained stable when more than 70 pounds was placed on an open drawer, while others tipped with less than half that weight

Composition of North Dakota's Economic Base: A Regional Analysis

The economic base of North Dakota and its eight substate regions has changed over the past couple of decades. This report takes an in-depth look at the economic base for each of these areas over the 1958-1984 period. Each of the regions has a unique composition of basic activities that have been responsible for its growth. Natural resource related activities, either in the form of agricultural or energy production, have been the largest source of real economic growth within the state. The purpose of this report is to identify the components of the economic base at substate levels and to show the changes in relative composition for these activities. Price and production data are presented to support and explain the changes that have occurred.Community/Rural/Urban Development, Production Economics,

Characterization of iodine particles with Volatilization-Humidification Tandem Differential Mobility Analyser (VH-TDMA), Raman and SEM techniques

Particles formed upon photo-oxidation of CH2I2 and particles of I2O5 and HIO3 have been studied using a Volatilisation and Humidification Tandem Differential Mobility Analyser (VH-TDMA) system. Volatilization and hygroscopic behaviour have been investigated as function of temperature (from 25 to 400 degrees Celsius), humidity (RH from 80 to 98%), initial aerosol sizes (from 27 to 100 nm mobility diameter) and in nitrogen or air as the sheath gasses. The volatility behaviour of particles formed upon photo-oxidation of CH2I2 is more similar to that of HIO3 particles in a filtered sheath air than in nitrogen, with the particle shrinkage occurring at 190 degrees Celsius and accompanied by hygroscopic growth. Despite its high solubility, HIO3 was found not to be hygroscopic at room temperature with no significant growth displayed until the thermodenuder temperature reached 200 degrees Celsius or above when the particles have transformed into I2O5. Diiodopentaoxide (I2O5) particles exhibit relatively low hygroscopic growth factors of 1.2-2 in the humidity range investigated. Scanning Electron Microscopy (SEM) of particles formed upon photo-oxidation of CH2I2 shows that their primary elemental components were iodine and oxygen in a stoichiometric ratio of approximately 1:2 with 10% error. Both Raman spectra and SEM show poor crystallinity for all the aerosols produced

Timing of Latest Eocene Molluscan Extinction Patterns in Mississippi

Molluscs removed from 12 bulk samples of the Yazoo Formation (upper Eocene), exposed in a quarry at Cynthia, Mississippi, are similar in com- position and diversity to those found in the underlying upper Eocene Moodys Branch Formation, when dif- ferences in outcrop area are considered (74% of the Yazoo species are also found in the Moodys Branch). This suggests there was no significant extinction during the late Eocene (at the P15/P16 biozone boundary) as has been reported for planktic foraminifera. Only 11.4% of the species from the Yazoo extend into the Oligocene Red Bluff Formation, suggesting a large molluscan extinction at or near the Eocene-Oligocene boundary. The presence in the lowermost Red Bluff of an assemblage with a relatively high diversity dominated by suspension-feeding bivalves suggests that the molluscan fauna had recovered from the extinction by the earliest Oli- gocene

Spatial Variation of Naticid Gastropod Predation in the Eocene of North-America

Although, the fossil record of naticid gastropod drilling has played an important role in the controversy over predator-prey evolution, little is known about variation of drilling frequencies within single horizons or how predation patterns are influenced by environmental variables. Without an understanding of spatial variation in drilling, temporal patterns in drilling are difficult to interpret. We surveyed 27,554 specimens of molluscs from the Cook Mountain interval (upper middle Eocene) and Jackson Group (late Eocene) of the U.S. Gulf and Atlantic Coastal Plain to document spatial variation in naticid drilling frequencies. The Jackson Group assemblages from the Moodys Branch and Yazoo formations were sampled along a depth gradient in order to compare drilling frequencies to environmental variables within a single climatic zone. There was a statistically significant difference between drilling frequency of the inner to middle shelf Moodys Branch Formation (mean = 8.3%) and the outer shelf Yazoo Formation (mean = 21.2%; chi square = 49.58, P ≪ 0.001), but there was no significant bathymetric trend in drilling frequencies among the five assemblages of the Moodys Branch. Drilling frequency was not related to substrate type within the Moodys Branch. Drilling, however, was correlated with species diversity of Moodys Branch assemblages (r = 0.50, P \u3c 0.01). Drilling frequency was significantly correlated with the percentage of naticids in each assemblage (r = 0.77, P \u3c 0.001) and the percentage of certain prey species of the bivalve families Lucinidae and Corbulidae, and the gastropod families Turritellidae and Hipponicidae (r = 0.80, P \u3c 0.001). These preferred species represented 40% of the naticid victims, but only 16% of the assemblages. Cook Mountain assemblages represented marine inner to middle shelf environments from Virginia, Alabama, Louisiana, and Texas. Naticid drilling frequencies of the entire molluscan fauna ranged from 6.8-38.7% with a mean of 22%. In the Cook Mountain, three preferred species (of the families Turritellidae, Lucinidae, and Noetiidae), representing 24% of the total individuals, accounted for 44% of the drilled individuals. As in the Moodys Branch Formation, Cook Mountain assemblages showed a significant correlation between relative abundance of preferred species and drilling frequency of samples (r = 0.585, P \u3c 0.05). The dependence of naticid drilling on the availability of preferred prey species indicates a possible behavioral inflexibility in naticid predation patterns. The Virginia Cook Mountain fauna exhibited significantly greater drilling frequencies (mean = 30.3%, n = 4 samples) than did the Gulf Coast assemblages (mean = 18.0%, n = 11 samples; Mann-Whitney U-test, P \u3c 0.01). This result is consistent with a trend found by some previous workers of an equatorward decrease in naticid drilling