Hydrocode modeling of the spallation process during hypervelocity impacts: Implications for the ejection of Martian meteorites

Hypervelocity ejection of material by impact spallation is considered a plausible mechanism for material exchange between two planetary bodies. We have modeled the spallation process during vertical impacts over a range of impact velocities from 6 to 21 km/s using both grid- and particle-based hydrocode models. The Tillotson equations of state, which are able to treat the nonlinear dependence of density on pressure and thermal pressure in the strongly shocked matter, were used to study the hydrodynamic and thermodynamic response after impacts. The effects of material strength and gravitational acceleration were not considered. A two-dimensional time-dependent pressure field within a 1.5-fold projectile radius from the impact point was investigated in cylindrical coordinates to address the generation of spalled material. A resolution test was also performed to reject ejected materials with peak pressures that were too low due to artificial viscosity. The relationship between ejection velocity veject and peak pressure Ppeak was also derived. Our approach shows that late stage acceleration in an ejecta curtain occurs due to the compressible nature of the ejecta, resulting in an ejection velocity that can be higher than the ideal maximum of the resultant particle velocity after passage of a shock wave. We also calculate the ejecta mass that can escape from a planet like Mars (i.e., veject higher than 5 km/s) that matches the petrographic constraints from Martian meteorites, and which occurs when Ppeak from 30-50 GPa. Although the mass of such ejecta is limited to from 0.1-1 percent of the projectile mass in vertical impacts, this is sufficient for spallation to have been a plausible mechanism for the ejection of Martian meteorites. Finally, we propose that impact spallation is a plausible mechanism for the generation of tektites.Comment: 67 pages, 28 figures, accepted for publication in Icaru

Electrosynthesis of acetate from inorganic carbon (HCO₃⁻) with simultaneous hydrogen production and Cd(II) removal in multifunctional microbial electrosynthesis systems (MES)

The simultaneous production of acetate from bicarbonate (from CO2 sequestration) and hydrogen gas, with concomitant removal of Cd(II) heavy metal in water is demonstrated in multifunctional metallurgical microbial electrosynthesis systems (MES) incorporating Cd(II) tolerant electrochemically active bacteria (EAB) (Ochrobactrum sp. X1, Pseudomonas sp. X3, Pseudomonas delhiensis X5, and Ochrobactrum anthropi X7). Strain X5 favored the production of acetate, while X7 preferred the production of hydrogen. The rate of Cd(II) removal by all EAB (1.20–1.32 mg/L/h), and the rates of acetate production by X5 (29.4 mg/L/d) and hydrogen evolution by X7 (0.0187 m3/m3/d) increased in the presence of a circuital current. The production of acetate and hydrogen was regulated by the release of extracellular polymeric substances (EPS), which also exhibited invariable catalytic activity toward the reduction of Cd(II) to Cd(0). The intracellular activities of glutathione (GSH), catalase (CAT), superoxide dismutase (SOD) and dehydrogenase were altered by the circuital current and Cd(II) concentration, and these regulated the products distribution. Such understanding enables the targeted manipulation of the MES operational conditions that favor the production of acetate from CO2 sequestration with simultaneous hydrogen production and removal/recovery of Cd(II) from metal-contaminated and organics-barren waters

Exclusively Gas-Phase Passivation of Native Oxide-Free Silicon(100) and Silicon(111) Surfaces

Reactions in the gas phase are of primary technological importance for applications in nano- and microfabrication technology and in the semiconductor industry. We present exclusively gas-phase protocols to chemically passivate oxide-free Si(111) and Si(100) surfaces with short-chain alkynes. The resulting surfaces showed equal or better oxidation resistance than most existing liquid-phase-derived surfaces and rivaled the outstanding stability of a full-coverage Si(111)–propenyl surface., The most stable surface (Si(111)–ethenyl) grew one-fifth of a monolayer of oxide (0.04 nm) after 1 month of air exposure. We monitored the regrowth of oxides on passivated Si(111) and Si(100) surfaces by X-ray photoelectron spectroscopy (XPS) and observed a significant crystal-orientation dependence of initial rates when total oxide thickness was below approximately one monolayer (0.2 nm). This difference was correlated with the desorption kinetics of residual surface Si–F bonds formed during HF treatment. We discuss applications of the technology and suggest future directions for process optimization

Properties of annual plant communities subjected to N addition

In October 2008, sixty 8×8m plots were randomly placed across an experimental area of 5,400 m2 in the center of the Gurbantunggut desert (44.876 N, 87.823 E), with an average separation distance of about 10 m. The plots had similar plant community composition and structure before the N treatments. From year 2008 to 2011, five N concentrations plus one control (without N) were randomly applied on the plots, totaling 10 replicates of each of the six concentrations. The rates of six N treatments were 0, 0.5, 1, 3, 6 and 24 g N m-2 a-1 (hereafter denoted as N0, N0.5, N1, N3, N6 and N24, respectively). The N treatments were applied in two equal pulses per year in March after snow thaw and October before snowfall every year, coinciding reasonably with a fall-spring pulses associated with rainy seasons, and with fertilization (and thus deposition) pulses in agricultural areas of the region. Each applied N treatment consisted of 2:1 molar ratio of NH4+: NO3- (as NH4NO3 and NH4Cl), in 3 L of water per plot (about 0.037 mm of rainfall equivalent) applied using a spray. Controls received an equivalent amount of water only. The first treatment began in October 2008 and were repeated every year after that to simulate long-term effects of N deposition. In each plot, we established one 1× 1 m permanent quadrat for the investigation of community composition and structure. The richness (number of species per plot) and density (number of individuals per plot) were measured in mid-spring (April), late spring (May – June), and summer (July - August) in each year after N treatments. These seasons were chosen because various life forms of plants reach their peak biomass during these periods. We calculated the evenness index J’ based on the number of individuals per species (Tuomisto, 2012). Peak aboveground biomass provides a good estimate of annual aboveground production in communities dominated by annual plants (Sala et al., 1988). We measured production three times each year, concurrent with community measures. We selected one 0.5×0.5 m quadrat (far from the permanent quadrat for community investigation) in each 8×8 m plot for the measurement of aboveground and belowground biomass. All plants from the quadrat were collected using spades. We separated shoot and root portions for each species in the lab (after washing adherent sand from roots using tap water), and measured the biomass after drying at 70 oC for 24 hours in the oven to obtain consistent weight. The aboveground biomass was the total shoot biomass of all annual plants (including ephemeroid plants). The belowground biomass was the total root biomass of all annual plants excluding ephemeroid plants. The ephemeroid plants were excluded because their roots were cloned together (two or more ramets fused together) and exist for several years. The root biomass of ephemeroids was significantly higher than other annual plants and significantly differed among quadrants, even before the start of the experiment. In order to use community structure as a variable in some analyses, data reduction was necessary. As a data reduction tool, we used nonmetric multidimensional scaling of total above and belowground biomass by species, based on the Bray-Curtis distance measure (McCune and Grace, 2002). Prior to ordination, we omitted any species that were present in fewer than 3 samples to reduce noise and omitted any samples that lacked any plant biomass because empty samples are incompatible with this distance measure. After these modifications, we performed a general relativization, rescaling the abundance of all species within a sample such that they summed to 1. We obtained a two-axes ordination and rotated it so that Axis 1 correlated with season, the apparent strongest driver of composition. We saved axis scores for each sample for use in our structural equation model

Large-Scale Single Particle and Cell Trapping based on Rotating Electric Field Induced-Charge Electroosmosis

We propose a simple, inexpensive microfluidic chip for large-scale trapping of single particles and cells based on induced-charge electroosmosis in a rotating electric field (ROT-ICEO). A central floating electrode array, was placed in the center of the gap between four driving electrodes with a quadrature configuration and used to immobilize single particles or cells. Cells were trapped on the electrode array by the interaction between ROT-ICEO flow and buoyancy flow. We experimentally optimized the efficiency of trapping single particles by investigating important parameters like particle or cell density and electric potential. Experimental and numerical results showed good agreement. The operation of the chip was verified by trapping single polystyrene (PS) microspheres with diameters of 5 and 20 μm and single yeast cells. The highest single particle occupancy of 73% was obtained using a floating electrode array with a diameter of 20 μm with an amplitude voltage of 5 V and frequency of 10 kHz for PS microbeads with a 5-μm diameter and density of 800 particles/μL. The ROT-ICEO flow could hold cells against fluid flows with a rate of less than 0.45 μL/min. This novel, simple, robust method to trap single cells has enormous potential in genetic and metabolic engineering

Site Occupancy and VUV–UV–Vis Photoluminescence of the Lanthanide Ions in BaY₂Si₃O₁₀

This work provides a scheme to investigate the site occupancy and the luminescence properties of lanthanide ions in BaY₂Si₃O₁₀. The Rietveld refinement of the samples indicates that the lanthanide ions preferably occupy the Y³⁺ sites in BaY₂Si₃O₁₀. It is confirmed that valence state of lanthanide ions is stable at +3 in all doping samples. The site-dependent spectroscopic properties of Ce³⁺ and Eu³⁺ are studied in VUV–UV–vis spectral region at low temperatures, and the polarization effect on Ce³⁺ luminescence decay is evaluated. The results indicate that the lanthanide ions experience the similar polarization effect when substituting the Y³⁺ sites in BaY₂Si₃O₁₀. The Stokes shift of Ce³⁺ luminescence becomes larger as Ce³⁺ doping content increases. Eu³⁺ f–f line-shape change has not been observed in the spectra as Eu³⁺ content increases. It demonstrates that the change of the electrostatic binding effect in the lattice has little effect on the ligand polarization of the central lanthanide ion. Finally, a mechanism is proposed to explain why the thermal-quenching of Ce³⁺ luminescence is negligible in BaY₂Si₃O₁₀ even if the temperature increases up to 500 K. The influence of dynamic ion–lattice interaction on luminescence properties of the lanthanide ions in BaY₂Si₃O₁₀ is discussed in detail

Structure Refinement and Two-Center Luminescence of Ca₃La₃(BO₃)₅:Ce³⁺ under VUV–UV Excitation

A series of Ca₃La_{3(1–<i>x</i>)}Ce_3<i>x</i>(BO₃)₅ phosphors were prepared by a high-temperature solid-state reaction technique. Rietveld refinement was performed using the powder X-ray diffraction (XRD) data, which shows occupation of Ce³⁺ on both Ca²⁺ and La³⁺ sites with a preferred location on the La³⁺ site over the Ca²⁺ site. The prepared samples contain minor second phase LaBO₃ with contents of ∼0.64–3.27 wt % from the Rietveld analysis. LaBO₃:1%Ce³⁺ was prepared as a single phase material and its excitation and emission bands were determined for identifying the influence of impurity LaBO₃:Ce³⁺ luminescence on the spectra of the Ca₃La_{3(1–<i>x</i>)}Ce_3<i>x</i>(BO₃)₅ samples. The luminescence properties of Ca₃La_{3(1–<i>x</i>)}Ce_3<i>x</i>(BO₃)₅ samples under vacuum ultraviolet (VUV) and UV excitation were investigated, which exhibited two-center luminescence of Ce³⁺, assigned to the Ce(1)³⁺ center in the La³⁺ site and Ce(2)³⁺ center in the Ca²⁺ site, taking into account the spectroscopic properties and the Rietveld refinement results. The influences of the doping concentration and the excitation wavelength on the luminescence of Ce³⁺ in Ca₃La_{3(1–<i>x</i>)}Ce_3<i>x</i>(BO₃)₅ are discussed together with the decay characteristics

Additional file 1 of Non-traumatic osteonecrosis of the femoral head induced by steroid and alcohol exposure is associated with intestinal flora alterations and metabolomic profiles

Supplementary Material

Structure Refinement and Two-Center Luminescence of Ca₃La₃(BO₃)₅:Ce³⁺ under VUV–UV Excitation

A series of Ca₃La_{3(1–<i>x</i>)}Ce_3<i>x</i>(BO₃)₅ phosphors were prepared by a high-temperature solid-state reaction technique. Rietveld refinement was performed using the powder X-ray diffraction (XRD) data, which shows occupation of Ce³⁺ on both Ca²⁺ and La³⁺ sites with a preferred location on the La³⁺ site over the Ca²⁺ site. The prepared samples contain minor second phase LaBO₃ with contents of ∼0.64–3.27 wt % from the Rietveld analysis. LaBO₃:1%Ce³⁺ was prepared as a single phase material and its excitation and emission bands were determined for identifying the influence of impurity LaBO₃:Ce³⁺ luminescence on the spectra of the Ca₃La_{3(1–<i>x</i>)}Ce_3<i>x</i>(BO₃)₅ samples. The luminescence properties of Ca₃La_{3(1–<i>x</i>)}Ce_3<i>x</i>(BO₃)₅ samples under vacuum ultraviolet (VUV) and UV excitation were investigated, which exhibited two-center luminescence of Ce³⁺, assigned to the Ce(1)³⁺ center in the La³⁺ site and Ce(2)³⁺ center in the Ca²⁺ site, taking into account the spectroscopic properties and the Rietveld refinement results. The influences of the doping concentration and the excitation wavelength on the luminescence of Ce³⁺ in Ca₃La_{3(1–<i>x</i>)}Ce_3<i>x</i>(BO₃)₅ are discussed together with the decay characteristics

Consequences of ET and MMCT on Luminescence of Ce³⁺-, Eu³⁺-, and Tb³⁺-doped LiYSiO₄

Ce³⁺, Eu³⁺, and Tb³⁺ singly doped, Ce³⁺-Tb³⁺, Tb³⁺-Eu³⁺, and Ce³⁺-Eu³⁺ doubly doped, as well as Ce³⁺-Tb³⁺-Eu³⁺ triply doped LiYSiO₄ phosphors were prepared by a high-temperature solid-state reaction technique. Rietveld refinement was performed to determine the structure of host compound. The cross-relaxation (CR) of Tb³⁺ is quantitatively analyzed with the Inokuti–Hirayama model of energy transfer (ET), and the site occupancy is confirmed by emission spectra of Eu³⁺. ET and metal–metal charge transfer (MMCT) are systematically investigated in Ce³⁺-Tb³⁺, Tb³⁺-Eu³⁺, and Ce³⁺-Eu³⁺ doubly doped systems. The combined effects of ET and MMCT on luminescence and emission color of Ce³⁺-Tb³⁺-Eu³⁺ triply doped samples are discussed in detail, showing that the photoluminescence emission is tunable in a large color gamut