bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of the effect of maize porridge fortified with grain amaranth or micronutrient powder containing NaFeEDTA on iron intake and status in Kenyan children
Authors: Macharia-Mutie Catherine W , Omusundi Agnes M , Mwai John M , Mwangi Alice M , Brouwer Inge D
Published: December 2012

Objective

Simulating the probable impact of grain amaranth and highly absorbable, low-Fe micronutrient powder (MNP) on Fe status in a potential target population is an essential step in choosing and developing an appropriate actual intervention.

Design

We simulated the potential effect of fortifying maize porridge with grain amaranth or MNP on the prevalence of inadequate Fe intake and Fe deficiency using data from two cross-sectional surveys. In the first survey (2008), dietary intake data were collected by two 24 h recalls (n197). Biochemical data (n70) were collected in the second survey (2010). A simulation with daily consumption for 80 d of non-fortified maize porridge (60 g of maize flour), amaranth-enriched porridge (80 g of grain amaranth–maize flour, 70:30 ratio) or maize porridge fortified with MNP (2·5 mg Fe as NaFeEDTA) was done.

Setting

Mwingi District, Kenya.

Subjects

Pre-school children aged 12–23 months.

Results

Prevalence of anaemia, Fe deficiency and Fe-deficiency anaemia was 49 %, 46 % and 24 %, respectively. Consumption of non-fortified, amaranth-enriched and MNP-fortified maize porridge was estimated to provide a median daily Fe intake of 8·6 mg, 17·5 mg and 11·1 mg, respectively. The prevalence of inadequate Fe intake was reduced to 35 % in the amaranth-enriched porridge group and 45 % in the MNP-fortified porridge group, while ferritin concentration was increased in both (by 1·82 (95 % CI 1·42, 2·34) μg/l and 1·80 (95 % CI 1·40, 2·31) μg/l, respectively;P< 0·005) compared with the non-fortified maize porridge group, resulting in a decreased prevalence of Fe deficiency (27 %) in the two fortification groups.

Conclusions

Addition of grain amaranth or low-Fe MNP to maize-based porridge has potential to improve Fe intake and status in pre-school children.
Three-Dimensional Structural Characterization of Nonwoven Fabrics
Authors: Venu Lalith B. Suragani , Shim Eunkyoung , Anantharamaiah Nagendra , Pourdeyhimi Behnam
Published: December 2012

Nonwoven materials are found in a gamut of critical applications. This is partly due to the fact that these structures can be produced at high speed and engineered to deliver unique functionality at low cost. The behavior of these materials is highly dependent on alignment of fibers within the structure. The ability to characterize and also to control the structure is important, but very challenging due to the complex nature of the structures. Thus, to date, focus has been placed mainly on two-dimensional analysis techniques for describing the behavior of nonwovens. This article demonstrates the utility of three-dimensional (3D) digital volumetric imaging technique for visualizing and characterizing a complex 3D class of nonwoven structures produced by hydroentanglement.
The impact of rain on ice nuclei populations at a forested site in Colorado
Authors: Prenni A. J. , Tobo Y. , Garcia E. , DeMott P. J. , Huffman J. A. , McCluskey C. S. , Kreidenweis S. M. , Prenni J. E. , Pöhlker C. , Pöschl U.
Published: December 2012

It has long been known that precipitation can impact atmospheric aerosol, altering number concentrations and size‐dependent composition. Such effects result from competing mechanisms: precipitation can remove particles through wet deposition, or precipitation can lead to the emission of particles through mechanical ejection, biological processes, or re‐suspension from associated wind gusts. These particles can feed back into the hydrologic cycle by serving as cloud nuclei. In this study, we investigated how precipitation at a forested site impacted the concentration and composition of ice nuclei (IN). We show that ground level IN concentrations were enhanced during rain events, with concentrations increasing by up to a factor of 40 during rain. We also show that a fraction of these IN were biological, with some of the IN identified using DNA sequencing. As these particles get entrained into the outflow of the storm, they may ultimately reach cloud levels, impacting precipitation of subsequent storms.
Statistics of bedload transport over steep slopes: Separation of time scales and collective motion
Authors: Heyman J. , Mettra F. , Ma H. B. , Ancey C.
Published: December 2012

Steep slope streams show large fluctuations of sediment discharge across several time scales. These fluctuations may be inherent to the internal dynamics of the sediment transport process. A probabilistic framework thus seems appropriate to analyze such a process. In this paper, we present an experimental study of bedload transport over a steep slope flume for small to moderate Shields numbers. The sampling technique allows the acquisition of high‐resolution time series of the solid discharge. The resolved time scales range from 10− 1 s up to 105 s. We show that two distinct time scales can be observed in the probability density function for the waiting time between moving particles. We make the point that the separation of time scales is related to collective dynamics. Proper statistics of a Markov process including collective entrainment are derived. The separation of time scales is recovered theoretically for low entrainment rates.
Regional variation of morphology of organized convection in the tropics and subtropics
Authors: Liu Chuntao , Zipser Edward
Published: December 2012

Properties of organized convection with large horizontal area (> 1000 km2) and with different horizontal structures in the tropics and subtropics are investigated by using 14 years of Tropical Rainfall Measuring Mission observations. First, the convective features (CFs) are defined as contiguous areas of convective precipitation detected by the Tropical Rainfall Measuring Mission precipitation radar. Using the minor and major axes of fitted ellipses, the morphology of the CFs are described as closer to a circular or a line shape. Regional variations and the properties of organized convection are examined with CFs with area>1000 km2 after categorizing them by their shapes. Organized convection tends to have larger extent and a higher fraction of near‐circular shapes over land than over ocean. Shallow organized convection with maximum radar echo top height below 4.5 km is found mainly over ocean and some coastal regions. Of all tropical oceans, most shallow organized convection is found over the east Pacific. The fraction of line shaped organized convection is higher over the ocean than over land, and is higher in the subtropics than in the tropics. More convective lines are found in winter than in summer over oceans, but more in summer over land. Organized convective lines are slightly less convectively intense indicated by lower 30 dBZ echo top heights and warmer 37 GHz brightness temperatures than those with near‐circular shapes. Orientations of organized convective lines are often aligned with fronts, dry lines, warm ocean currents, coastlines, and mountain slopes. Over the subtropics, organized convective lines are tilted more east‐west over land, and more north‐south over oceans. The largest and the most intense convective lines are found over central Africa, Argentina, and southeast U.S. over land, and over several warm currents in subtropical oceans.
Zr‐Hf‐Ta fractionation during lunar evolution
Authors: Hughes S. S. , Schmitt R. A.
Published: December 2012

Zr/Hf ratios and other elemental data for 68 lunar basalt, KREEP, and glass samples were obtained by coincidence‐anticoincidence counting and normal counting techniques during instrumental neutron activation analyses. Zr/Hf ratios indicate a complementary relation between a mean Zr/Hf ratio of 41.0±0.4 for KREEP and the mean ratios of 30–32 in Apollo 11, 12, and 17 mare basalts. The uniformity of Zr/Hf in 20 Apollo 14, 16, and 17 KREEP samples is consistent with petrogenesis of KREEP compositions from a single major source. The observed complementary ratios require greater Zr‐Hf fractionation than what is predicted by lunar evolutionary models and presently known distribution coefficients. The difference requires that either (1) ilmenite and armalcolite. the most predominant phases conducive to Zr‐Hf fractionation, begin to crystallize earlier and in greater amounts than is presently assumed, or (2) the relative partitioning of Hf over Zr in Ti‐oxides and/or major minerals and/or spinels is greater than what is observed in natural or synthetic systems. Complementary ratios also support a primordial Zr/Hf ratio of ∼35, represented by the E‐C‐O (enstatite, C2 and C3 carbonaceous, and ordinary) chondrites. Compiled Ta and Hf data from this laboratory indicate a well‐defined Ta/Hf trend for most Apollo mare basalts and Apollo 14 KREEP. Apollo 11 B3 and Apollo 17 basalts define an alternate trend of higher Ta/Hf that we attribute to relatively higher Ta in assimilated Ti‐bearing urKREEP residual phases due to the oxidation of Ta+4 to Ta+5 under elevated f02‐Apollo 15, 16, and 17 KREEP samples exhibit lower Ta/Hf ratios relative to the main trend and have a complementary relation to late‐stage Ti‐bearing cumulates with enhanced Ta/Hf.
Multistage exposure history of the 74261 soil constituents
Authors: Eugster O.
Published: December 2012

Gray soil 74261 was collected on the rim of Shorty crater in the Taurus Littrow valley. This soil is of particular interest because it may represent old lunar regolith material The cosmic ray exposure history and the isotopic composition of the trapped noble gases of clinopyroxene, plagioclase, basalt, ropy glass, and orange glass separates from the 74261 soil were investigated. Grain size separates from bulk soil were studied in order to determine the isotopic composition of the trapped noble gases. All constituents of this soil experienced an exposure to cosmic rays prior to the excavation by the Shorty crater formation 17 m.y. ago. Except for the orange glasses, all soil constituents were preexposed for about 370 m.y. at an average shielding depth of 75 g/cm2. The orange glasses experienced a preexposure for 90 m.y. at about 60 g/cm2 depth. The time when the preexposure occurred was riot determined because the fission Xe component could not be derived with sufficient precision for 235U‐136Xe dating. The relatively high (40Ar/36Ar)11 ratio of 5.8 to 8.3 indicates, however, that the preexposure to volatiles in the lunar atmosphere and to solar and cosmic radiations occurred early in the history cf the moon, perhaps about 3 aeons ago. In such a scenario the 74261 soil was buried after the preexposure period beneath some shielding material until it was reexcavated by the Shorty crater impact.
An experimental investigation of agglutinate melting mechanisms: Shocked mixtures of sodium and potassium feldspars
Authors: Simon S. B. , Papike J. J. , Hörz F. , See T. H.
Published: December 2012

We report the results of an experiment designed to test the validity of the model for agglutinate formation involving fusion of the finest fraction or F3 [Papike et al., 1981]. Impact glasses were formed from various mixes of orthoclase and albite powders, which were used as analogs for soils with chemically contrasting coarse and fine fractions. Shock pressures ranged from 31.8 GPa to 78.0 GPa (318–780 kbar). Results show that the composition of the finest soil fraction is the dominant factor in displacing the composition of the impact melt (agglutinate glass) from that of the bulk. Other factors are degree of shock, amount of melt, and volatile loss. A soil with no fine fraction displays only the effects of volatile loss whereas in other runs the glasses are compositionally displaced away from the bulk and toward the finest fraction. As predicted by the model, the lower pressure melts are the most fractionated; higher pressure is accompanied by increased melting causing glass compositions to approach the bulk. In general, the systematics predicted by the model are observed and it appears that the fusion of the finest fraction model is valid.
Cooling history of some Antarctic ureilites
Authors: Miyamoto Masamichi , Takeda Hiroshi , Toyoda Hiromi
Published: December 2012

To obtain some constraints on the cooling histories of ureilites, we have studied the chemical zoning of olivines and the compositional variations of pyroxenes in the PCA82506, Y790981, and ALH77257 ureilites using an electron microprobe. Fayalite components and CaO contents in olivines show a gradual decrease toward the rims. The MnO/FeO variation of ureilite pyroxenes shows a subtle anticorrelation that is probably related to the redox reaction during their original crystallization. The chemical variation within a grain of Y790981 pigeonites may be attributed to partial melting due to shock heating. Cooling rates of 2–6°C/hour have been obtained from diffusional calculations based on the reverse zoning profile of Fa components at the grain boundary of ureilite olivines. We assume that iron diffusion controls the reduction reaction, although the reduction process may be more complex. Because iron diffusion is slower in pyroxene than in olivine, ureilite pigeonite would not show chemical zoning by reduction if their cooling rates were faster than about 1°C/hour. This result is consistent with impact‐produced excavation of the ureilite parent mass.
The Leoville (CV3) accretionary breccia
Authors: Kracher Alfred , Keil Klaus , Kallemeyn G. W. , Wasson J. T. , Clayton R. N. , Huss G. I.
Published: December 2012

Leoville is a CV3 chondrite that contains a large variety of inclusions Besides refractory inclusions resembling those in Allende, fine‐grained, dark inclusions are especially prominent. Same of these are xenoliths of material very similar to CM chondrites in texture, bulk composition, and oxygen isotopes, However, they show an unusually large range in the degree of hydrous alteration. Other dark inclusions are similar to host matrix. The CV3 host of this breccia is similar to other CV chondrites, although less metamorphosed than Allende. We suggest that Leoville is a typical accretionary breccia whose parent body accreted after the CM‐like material represented by the xenoliths had formed and undergone alteration. After accretion Leoville suffered severe deformation, leading to foliation stronger than in any other chondrite, but the nature of the event that caused this remains unclear.
Apollo 14 Mare basalts: Petrology and geochemistry of clasts from Consortium Breccia 14321
Authors: Shervais John W. , Taylor Lawrence A. , Lindstrom Marilyn M.
Published: December 2012

Eleven mare basalt clasts have been extracted from polymict lunar breccia 14321 for a combined petrologic and geochemical study by our consortium. Ten of these clasts are high‐Al, low‐Ti mare basalts similar to those discovered previously at Apollo 14. The other is a highly evolved tridymite ferrobasalt with low Al and intermediate Ti contents. A high‐Al, ilmenite ferrobasalt from lunar breccia 14305 is the most evolved high‐Al basalt described from the Apollo 14 site. The major and trace element characteristics of the basalts studied here allow them to be grouped into five compositional types that range from LREE‐depleted to LREE‐enriched. Some of these types may be related by varying percents of partial melting of the same source, but at least two separate sources that differ by a factor of two in incompatible trace element concentrations are required. The “14321‐type” basalts and vitrophyres have steep chondritenormalized HREE slopes and may have formed by assimilation of “Intermediate‐K Fra Mauro” KREEP, which is presumed to represent a partial melt of the lower crust. The age of these basalts (> 3.9 aeons) suggests that mare volcanism played an important role in the evolution of the early lunar crust.
The depths of the Mare basalt source region
Authors: Binder Alan B.
Published: December 2012

Chemical data for the parental magmas of the nine known VLT Array I pyroclastic glasses show statistically significant trends due to olivine (∼Fo83) control during their formation by partial melting. The compositional scatter is largely due to compositional variations in the source regions on the ±1% level. This compositional scatter is small when one considers that the scale of the source region is up to 1000 km, but is sufficient to make positive identification of the residual phase(s) in the source regions difficult. Nevertheless, when the effects of the scatter are properly modeled, it is relatively clear that olivine is the residual phase in the source region. Hence these data and additional constraints indicate that the source regions are at shallow depths in the moon.
Chemistry and petrology of Apollo 12 Drive Tube 12027
Authors: Smith Monty R. , Laul J. C. , Simon Steven B. , Papike J. J.
Published: December 2012

Modal and chemical data for 31 major, minor, and trace elements obtained by INAA for soils from four (∼5 cm) depth intervals of drive tube 12027 show three compositional units within the core. The upper ∼2.5 cm of 12027 represent part of the Sharp crater rim crest deposit, which has a total thickness of ∼23 cm. Chemical differences are attributed to addition of local mare rocks to the upper 2 cm and KREEPy material to the lower stratigraphic layer (14–17 cm depth). The coarser fractions (1000‐90, 90‐20, and 20‐10 pm) are compositionally similar to each other but quite different from the < 10‐μm fine fractions, which are more feldspathic and enriched in incompatible (LIL) elements. Correlation between fused soil contents and LIL enrichments of the coarse fractions strongly suggests that agglutinates are derived from the fine fraction, thus supporting the fusion of the finest fraction (F3) model. The trench soil 12033, from ∼15 cm depth, is very similar to the 15.5‐16 cm soil of core 12027, indicating that the Apollo 12 regolith exhibits KREEP enrichments at various depths and that exotic KREEPy ejecta are wide spread at the Apollo 12 site.
The formation of an impact‐generated H2O atmosphere and its implications for the early thermal history of the Earth
Authors: Abe Yutaka , Matsui Takafumi
Published: December 2012

During accretion of the earth by planetesimal impacts, shock degassing of volatile materials occurs, and a proto‐atmosphere is formed. Once such an impact‐generated atmosphere is formed, the surface temperature of the earth growing by planetesimal impact increases due to the blanketing effect of the atmosphere. We show that the surface of the accreting earth was covered entirely by a “magma ocean.” This suggests that the differentiation of the earth proceeds under very low pressure and high temperature conditions during its accretion stage. This places a severe constraint on the amount of volatiles in the mantle, and the formation time of the atmosphere and ocean of the earth.
Two‐stage models for lunar and terrestrial anorthosites: Petrogenesis without a magma ocean
Authors: Longhi John , Ashwal Lewis D.
Published: December 2012

Two‐stage diapiric models for lunar ferroan anorthosites and terrestrial massif anorthosites are examined. The lunar model is developed to explain early lunar differentiation in the absence of a magma ocean. If correct, the terrestrial model serves as an analog for the development of lunar anorthositic diapirs. There is field and textural evidence of transport of mostly crystalline anorthositic material within the terrestrial complexes. This evidence, combined with the absence of anorthositic lavas and phase equilibrium constraints inhibiting the production of hyperaluminous magmas, is consistent with the detachment of plagioclase‐rich crystalline mushes from large, uppermost mantle plutons and multiple diapiric intrusion of these mushes into the upper sialic crust with attendant anatexis. Rudimentary dynamical calculations suggest that a simple, single‐layer source for the diapirs is improbable: either there were several parental magma chambers or there was a single large chamber that was repeatedly replenished. The lunar model is a development of Wetherill's (1975) suggestion that, following accretion, the outer portion of the moon consisted of a stack of overlapping layered intrusions and that reheating of these intrusions mobilized their anorthositic layers, which intruded upwards to produce the anorthositic lunar crust. Dynamical calculations show that gravitational instabilities in anorthositic layers (≤ 1 km thick) could develop into diapirs on a reasonable time scale (50‐100 m.y.) only if the outer portion of the moon was partially remelted. We suggest that partial melting of the interior due to the decay of long‐lived radionuclides with the subsequent onset of global convection heated the stack of intrusions from below, thus causing melting and allowing the anorthositic diapirs to grow and ascend fairly rapidly. As the convecting zone thickened, a mass expulsion of anorthositic material out of the lunar interior may have occurred.
Basaltic volcanism on the eucrite parent body: Petrology and chemistry of the polymict eucrite ALHA80102
Authors: Treiman Allan H. , Drake Michael J.
Published: December 2012

The polymict eucrite meteorite ALHA80102 i s an unequilibrated breccia of basaltic and gabbroic clasts in a fragmental matrix. Clasts include basalts of many textural types, cumulate gabbro, black “glass,” and ferroan troctolite (plagioclase, silica, Fe‐rich olivine, ilmenite, mesostasis). Ferroan troctolite has not been previously reported from eucrites or howardites; it is interpreted as the end‐product of fractional crystallization of eucritic magmas. Bulk and trace element compositions (by electron microprobe and INAA) of clasts and matrix from ALHA80102 are similar to those of other eucrites; the meteorite contains clasts similar to Juvinas and to Stannern. A clast of cumulate eucrite gabbro is enriched in the light rare earths (La/Lu=2XCI). This clast is interpreted as an unrepresentative sample of metamorphically equilibrated gabbro; LREE‐enriched magmas need not be invoked. ALHA80102 is similar to other polymict eucrites from the Allan Hills and may be paired with ALHA76005, ALHA77302, and ALHA78040.
Chemical zoning and homogenization of pasamonte‐type pyroxene and their bearing on thermal metamorphism of a Howardite parent body
Authors: Miyamoto Masamichi , Duke Michael B. , McKay David S.
Published: December 2012

We studied thermal metamorphism in the surface layer of a eucrite parent body by examining pyroxene zoning. Ca‐Mg‐Fe zoning of pyroxenes in the Pasamonte eucrite can be classified into three types: type 1 with a core composition of Ca5Mg62Fe32 and rim of Ca41Mg20Fe4o; type 2 with core of Ca5Mg62Fe32 and rim of Ca25Mg34Fe41; and type 3 with core of Ca5Mg66Fe29 and rim of Ca7Mg32Fe61. Type 1 typically occurs adjacent to a mesostasis, type 2 typically occurs adjacent to a surrounding plagioclase, and type 3 is common in pyroxenes in the matrix. Pasamonte is less metamorphosed than previously believed because of the wide range of composition of zoned pyroxenes. On the basis of Ca‐Mg‐Fe variation data, we have calculated the degree of homogenization of zoned pyroxenes by numerically solving the diffusion equation. A Pasamonte‐type pyroxene may yield a Juvinas‐type pyroxene by thermal metamorphism. The homogenization of Juvinas pyroxene could not have taken place during initial cooling and may be related to reheating events, although our calculation rests upon some assumptions.
Carbon isotopes in three SNC meteorites
Authors: Carr R. H. , Wright I. P. , Pillinger C. T.
Published: December 2012

Samples of three SNC meteorites —Shergotty, Chassigny, and Elephant Moraine (EETA 79001)— have been analysed for their contents and stable isotopic compositions of carbon using stepped combustion in an attempt to resolve indigenous components from terrestrial contaminants. The rarity of most of the SNC meteorites precludes the use of large samples for analysis; hence carbon isotopic compositions have been determined by static mass spectrometry. In all three cases, ca. 90% of the carbon was liberated below 500°C; the isotopic composition of this material being strongly suggestive of terrestrial contamination. At higher extraction temperatures, a range in values of −11 to −41% was found which, although not uncommon for carbon in terrestrial igneous rocks, is clearly distinct from the values postulated for the “bulk” Earth (δ13C ca. −5%). The presence of several carbonaceous components was inferred from the data, although only tentative suggestions can be made on the nature of most of them. Certain similarities in the carbon isotope versus temperature profiles are observed that may indicate a common origin for the three meteorites, but the lack of isotopic data from analogous terrestrial rocks and the absence of petrographic evidence of carbonaceous material in the SNC's remains an obstacle to the complete interpretation of the present results.
Fluid inclusions in stony meteorites—A cautionary note
Authors: Rudnick R. L. , Ashwal L. D. , Henry D. J. , Gibson E. K. , Roedder E. , Belkin H. E. , Colucci M. T.
Published: December 2012

Newly discovered fluid inclusions in thin sections of Bjurböle chondrules, shergottite EETA79001, lunar meteorite ALHA81005, and Apollo 16 glasses possess physical properties similar to those of fluid inclusions found in thin sections of five stony meteorites recently described by Warner et al. (1983). The distribution and physical properties of these new fluid inclusions indicate they may be artifacts of thin section preparation; we suggest that saw coolant was sucked into vacuum vesicles in glasses and minerals through submicroscopic fractures produced during sawing. The similarities between these fluid inclusions and fluid inclusions previously described by Warner et al. (1983) lead us to conclude that many of the fluid inclusions reported earlier may be artifacts. Consequently, the origin of any fluid inclusions observed in thin sections of extraterrestrial materials must be interpreted with caution. The most probable true extraterrestrial fluid inclusions are those that have been observed in grains prepared without exposure to liquids of any kind.
Analysis of segregation trends observed in iron meteorites using measured distribution coefficients
Authors: Sellamuthu R. , Goldstein J. I.
Published: December 2012

Fe‐Ni alloys of meteoritic composition were solidified by a plane front solidification technique. Distribution coefficients of Ni, P, Ir, Ge, and Cu were determined from the composition data of the plane front solidified alloys. Equations that describe the distribution coefficients (F, Ni, Ir, Ge, and Cu) as a function of S and P content as well as S to P ratio were used to calculate solute partitioning between solid and liquid during the solidification of IIAB, I1IAB, and IVA parent bodies. The calculated P versus Ni, Ir versus Ni, Ge versus Ni, and Cu versus Ni trends are in good agreement with the observed meteorite data for each chemical group. We conclude that each chemical grbup formed as a single molten pool in a parent body and that solute partitioning that occurred during solidification is responsible for the observed compositional trends within a single meteorite group.
The evolution of partially differentiated planetesimals: Evidence from iron meteorite groups IAB and IIICD
Authors: Kracher Alfred
Published: December 2012

Group IAB irons probably come from a parent body that partially differentiated into a sulfur‐rich molten core and a primitive silicate outer layer in which only minor or localized melting occurred. Although the complexity of meteorites from this parent body or bodies (irons with and without massive silicate inclusions, stony meteorites like Winona, sulfide‐rich meteorites like Mundrabilla, etc.) implies a complicated history, the partial differentiation model is consistent with most properties of these meteorites. The behavior of five model parent bodies of different composition during heating to 1400 K (the temperature recorded in many I AB silicates) shows that meteorites like IAB irons can form by this process. Sulfide‐rich parent bodies differentiate into a liquid, S‐rich core and a primitive, metal‐bearing mantle around 1230 K, but in parent bodies lower in sulfide abundance this process may be delayed until minor melting of silicates occurs (1370 ± 30 K). In most cases any silicate melt that may have formed resolidified in situ. The sulfide melt fractionally crystallized along the (Fe,Ni)‐FeS cotectic. Some melt was injected into silicates to form Copiapo‐type breccias. Considerations of graphite‐metal‐silicate equilibrium, and the retention of noble gases suggest that brecciated IABs formed at depth inside a moderately large (a few tens to a hundred kilometers) parent body. The correlation of I‐Xe ages with Ni content is interpreted as the result of an excess 129Xe component associated with the S‐rich melt, which increases with melt evolution.
A model for GCR‐particle fluxes in stony meteorites and production rates of cosmogenic nuclides
Authors: Reedy R. C.
Published: December 2012

A model is presented for the differential fluxes of galactic cosmic ray (GCR) particles with energies above 1 MeV inside any spherical stony meteorite as a function of the meteorite's preatmospheric radius and the sample's depth. This model is based on the Reedy‐Arnold equations for the energy‐dependent fluxes of GCR particles in the moon and is an extension of flux parameters that were derived for several meteorites of various sizes. This flux model is used to calculate the production rates of many cosmogenic nuclides as a function of radius and depth. The peak production rates for most nuclides that are created by the reactions of energetic GCR particles occur near the centers of meteorites with radii of 40 to 70 g cm−2. The calculated production rates usually agree well with measurements of cosmogenic nuclides in most meteorites. Although the model has some limitations, it reproduces well the basic trends observed for the depth‐dependent production of cosmogenic nuclides in stony meteorites of various radii. Some of these production profiles are different from those of other calculations. The chemical dependence of the production rates for several nuclides varies with size and depth.
Quantitative analysis of planetary reflectance spectra with principal components analysis
Authors: Johnson Paul E. , Smith Milton O. , Adams John B.
Published: December 2012

A technique is presented for quantitative analysis of planetary reflectance spectra as mixtures of particles on microscopic and macroscopic scales using principal components analysis. This technique allows for determination of the endmembers being mixed, their abundance, and the scale of mixing, as well as other physical parameters. Eighteen lunar telescopic reflectance spectra of the Copernicus crater region, from 600 nm to 1800 nm in wavelength, are modeled in terms of five likely endmembers: mare basalt, mature mare soil, anorthosite, mature highland soil, and clinopyroxene. These endmembers were chosen from a similar analysis of 92 lunar soil and rock samples. The models fit the data to within 2% rms. It is found that the goodness of fit is marginally better for intimate mixing over macroscopic mixing.
A new Monte Carlo model of lunar megaregolith development
Authors: Cashore Jac , Woronow Alex
Published: December 2012

A new Monte Carlo model is used to examine the development of the lunar megaregolith through impact cratering processes. The computer code incorporates some of the techniques used in earlier models; however, it also solves some notable problems in those earlier models. The difficult problem of “edge effects” in computer modeling has been resolved in this model. Additionally, more recent morphological information on crater geometries and ejecta blanket geometry are included in this model along with current information on the crater production function. The morphologies now contribute to the evolving landscape such that each new impact encounters a more topographically realistic terrain. This improved model predicts greater minimum megaregolith thicknesses than did the earlier models. The increase results mainly from three factors: (1) our use of the observed lunar highlands crater size‐frequency curve as the production function, (2) the retention of topographic information as cratering proceeds, and (3) the differences in the crater bowl and ejecta geometries. If the 25 km seismic horizon on the moon is attributable to the bottom of the crater‐excavated material, then the highlands appear to have suffered a bombardment of two to five times the number of craters presently preserved on the surface.
Recovering crater production functions from densely cratered surfaces
Authors: Woronow A.
Published: December 2012

Two techniques proposed for the recovery of the crater‐production functions on densely cratered surfaces have been appraised. The first technique classifies craters according to their degree of nm preservation, then interprets the statistics of the freshest craters as closely mimicking the full population's production function. Although commonly practiced, in fact, this method is demonstrably misleading for densely cratered surfaces. The second technique uses a weighting scheme to recover the production function. Each crater diameter measured is weighted by the fraction of the crater that remains unoverlapped by subsequent impacts. While this method is theoretically sound even at saturation crater densities, it too fails at high densities due to practical difficulties. For this technique to work effectively, one would have to be able to recognize and accurately measure the diameters of craters having less than 10% of their nms remaining, a feat beyond reasonable expectation.
Human cytoplasmic ProX edits mischarged tRNAPro with amino acid but not tRNA specificity
Authors: Ruan Liang-Liang , Zhou Xiao-Long , Tan Min , Wang En-Duo
Published: December 2012

aaRSs (aminoacyl-tRNA synthetases) are responsible for ensuring the fidelity of the genetic code translation by accurately linking a particular amino acid to its cognate tRNA isoacceptor. To ensure accuracy of protein biosynthesis, some aaRSs have evolved an editing process to remove mischarged tRNA. The hydrolysis of the mischarged tRNA usually occurs in an editing domain, which is inserted into or appended to the main body of the aaRS. In addition, autonomous, editing domain-homologous proteins can also trans-edit mischarged tRNA in concert or in compensating for the editing function of its corresponding aaRS. The freestanding ProX is a homologue of the editing domain of bacterial ProRS (prolyl-tRNA synthetase). In the present study, we cloned for the first time a gene encoding HsProX (human cytoplasmic ProX) and purified the expressed recombinant protein. The catalytic specificity of HsProX for non-cognate amino acids and identity elements on tRNAPro for editing were also investigated. We found that HsProX could deacylate mischarged Ala-tRNAPro, but not Cys-HstRNAUGGPro, and specifically targeted the alanine moiety of Ala-tRNAPro. The importance of the CCA76 end of the tRNA for deacylation activity and key amino acid residues in HsProX for its editing function were also identified.
Effect of high-intensity x-ray radiation on Bragg diffraction in silicon and diamond
Authors: Hau-Riege Stefan P. , Pardini Tommaso
Published: December 2012

We simulated the Bragg reflection of high-intensity short x-ray pulses from single-crystal silicon and diamond by coupling tight-binding-molecular dynamics with a simple atomic kinetics model. We found that even when the pulse-averaged Bragg intensity degrades significantly, the reflectivity drops only slightly at the beginning of the pulse until the lattice is disordered by non-thermal melting. These results suggest that Bragg reflectors could produce shortened x-ray pulses through temporal slicing.
Critical tensile strain and water vapor transmission rate for nanolaminate films grown using Al2O3 atomic layer deposition and alucone molecular layer deposition
Authors: Jen Shih-Hui , Lee Byoung H. , George Steven M. , McLean Robert S. , Carcia Peter F.
Published: December 2012

Critical tensile strains (CTSs) and water vapor transmission rates (WVTRs) were measured for nanolaminate films grown on polyimide substrates using Al2O3 atomic layer deposition (ALD) and alucone molecular layer deposition (MLD). Nanolaminate composition was controlled by varying the ratio of ALD:MLD cycles during film growth. For ∼100 nm film thicknesses, the CTS obtained its highest value of ∼1.0% for the 3:1 nanolaminate. The WVTR decreased dramatically versus nanolaminate composition and reached the measurement sensitivity limit at WVTR ∼1 × 10−4 g/(m2day) for the 7:2, 5:1, and 6:1 nanolaminates. The ALD:MLD nanolaminates may be useful as flexible gas/vapor diffusion barriers on polymers.
Lambertian white top-emitting organic light emitting device with carbon nanotube cathode
Authors: Freitag P. , Zakhidov Al. A. , Luessem B. , Zakhidov A. A. , Leo K.
Published: December 2012

We demonstrate that white organic light emitting devices (OLEDs) with top carbon nanotube (CNT) electrodes show almost no microcavity effect and exhibit essentially Lambertian emission. CNT top electrodes were applied by direct lamination of multiwall CNT sheets onto white small molecule OLED stack. The devices show an external quantum efficiency of 1.5% and high color rendering index of 70. Due to elimination of the cavity effect, the devices show good color stability for different viewing angles. Thus, CNT electrodes are a viable alternative to thin semitransparent metallic films, where the strong cavity effect causes spectral shift and non-Lambertian angular dependence. Our method of the device fabrication is simple yet effective and compatible with virtually any small molecule organic semiconductor stack. It is also compatible with flexible substrates and roll-to-roll fabrication.
The structure of dislocations in (In,Al,Ga)N wurtzite films grown epitaxially on (0001) or (112¯2) GaN or AlN substrates
Authors: Jones K. A. , Batyrev I. G.
Published: December 2012

When dislocations have to be nucleated in the film to accommodate the lattice mismatch with the substrate, the shear stress acting in the glide plane, projection of the edge component of the Burgers vector lying in the growth plane, shear stress required for the dislocation to glide, and ability to decompose into partial dislocation pairs with an associated stacking fault are considered. This is done for growth on the (0001) or (112¯2) substrates by calculating the angle the slip plane, h, makes with the growth plane, length of the Burgers vector, b, angle between b and the dislocation line, l, projection of b onto the normal to l lying in the growth plane, and planar density of h. The planar density is used as a measure of the shear stress required to move the dislocation, and it is computed by determining the interplanar spacing, d, and accounting for the atoms that lie in parallel planes, which are made possible by the fact that the wurtzite unit cell contains four atoms per lattice point. Only dislocations with pyramidal glide planes are considered for growth on the (0001) substrate because the plane strain generated by the lattice mismatch does not generate any shear stress in the basal or prismatic planes. Only one member of the family of planes is considerate for this growth plane because of its high symmetry. For growth on the (112¯2) plane both slip in the basal plane and the prismatic plane normal to the Burgers vector in it are examined.
Evidence of exchange bias effect and surface spin glass ordering in electron doped Sm0.09Ca0.91MnO3 nanomanganites
Authors: Giri S. K. , Poddar A. , Nath T. K.
Published: December 2012

We report here the magnetic properties of slightly electron-doped Sm1−xCaxMnO3 manganites with the doping level of x = 0.91. Exchange bias effect has been observed in the nanomanagnites system and can be tuned by the strength of cooling field. Magnetic training effect as well as systematic shift of vertical and horizontal magnetic hysteresis loops as a function of temperature and cooling field clearly indicate the exchange bias effect. Low field dc magnetization and frequency dependent ac susceptibility results of nanomanganites suggest the onset of glassy like phase at ∼109 K. We also find spin glass like slow relaxation of magnetization, aging, and memory phenomena in the nanometric sample compared to its bulk counterpart. The enhancement of this glassy phase has been argued to be due to the modification of the phase separated state on size reduction. Magnetic training effect has been explained through the spin relaxation model. A phenomenological core-shell type model has been ascribed to an exchange coupling between the glassy ferromagnetic shell and antiferromagnetic core of Sm0.09Ca0.91MnO3 nanomanganites mainly on the basis of uncompensated surface spins. Results suggest that the intrinsic phase inhomogeneity due to the surface effects of this nanomanganite may cause exchange anisotropy, which is of special interests for potential application in multifunctional spintronic devices.
Surface-enhanced Raman scattering (SERS) based on copper vanadate nanoribbon substrate: A direct bio-detection without surface functionalization
Authors: Lin Haiyang , Shao Qi , Yin Kui , Que Ronghui , Shao Mingwang , Lee Shuit-Tong
Published: December 2012

Copper vanadate nanoribbons were synthesized via a hydrothermal method and served as surface-enhanced Raman scattering substrates with an enhancement factor of 1450 in the detection 1 × 10−5 M Rhodamine 6 G solution. This substrate also exhibited satisfied results in the non-functionalized bio-detection of 1 × 10−2 M tyrosine solution, owing to its interaction to amino acids and vast surface area to further the interaction.
Numerical simulations of electrostatic interactions between an atomic force microscopy tip and a dielectric sample in presence of buried nano-particles
Authors: Arinero R. , Riedel C. , Guasch C.
Published: December 2012

Nanoscale tomography is an outstanding challenge with an urgent need in materials science. In this context, electrostatic force microscopy offers the possibility to investigate nanoparticles buried inside dielectric films. In this paper, finite element modeling has been performed to analyze their detectability with regard to both particles features (size and depth) and dielectric permittivity of the medium. In the case of charged particles, a sign dependence of the detectability was demonstrated by means of observations of local electric fields and equipotential lines deformations.
Exchange bias effect in CoFe2O4-Cr2O3 nanocomposite embedded in SiO2 matrix
Authors: Borgohain Chandan , Mishra Debabrata , Sarma K. C. , Phukan Prodeep
Published: December 2012

A nanogranular system composed of CoFe2O4-Cr2O3 core-shell nanoparticles (embedded in SiO2 matrix) having average particle size of 35 ± 5 nm was prepared by chemical synthesis. Structural characterizations by x-ray diffraction, Transmission Electron Microscope (TEM) show highly crystalline phase of these nanocomposites. High resolution TEM images show distorted and modified grain boundary region. CoFe2O4-Cr2O3 nanocomposites show excellent positive exchange bias effect after field cooling at 100 Oe of applied field. Both the exchange bias field and vertical shift in magnetization loop has been observed in this system below 300 K after field cooling. There is a positive loop shift of about 5 kOe along the field axis at 20 K in this system while the vertical shift is nearly 100% owing to the strong exchange bias effect. The exchange bias effect has been explained in terms of the different magnetic exchange interactions and modified grain boundary effect of CoFe2O4-Cr2O3 nanocomposites. The role of spin glass like phase and surface effects of the nanocomposite on the vertical shift of the hysteresis loop and the sharp increase of exchange bias field (HEB) has also been discussed.
Consolidation of Bi-2223 superconducting powders by spark plasma sintering
Authors: Govea-Alcaide E. , Machado I. F. , Bertolete-Carneiro M. , Muné P. , Jardim R. F.
Published: December 2012

The spark plasma sintering (SPS) technique, by using a compacting pressure of 50 MPa, was used to consolidate pre-reacted powders of Bi1.65Pb0.35Sr2Ca2Cu3O10+δ (Bi-2223). The influence of the consolidation temperature, TD, on the structural and electrical properties has been investigated and compared with those of a reference sample synthesized by the traditional solid-state reaction method and subjected to the same compacting pressure. From the X-ray diffraction patterns, performed in both powder and pellet samples, we have found that the dominant phase is the Bi-2223 in all samples but traces of the Bi2Sr2CaCu2O8+x (Bi-2212) were identified. Their relative density were ∼85 % of the theoretical density and the temperature dependence of the electrical resistivity, ρ(T), indicated that increasing TD results in samples with low oxygen content because the SPS is performed in vacuum. Features of the ρ(T) data, as the occurrence of normal-state semiconductor-like behavior of ρ(T) and the double resistive superconducting transition, are consistent with samples comprised of grains with shell-core morphology in which the shell is oxygen deficient. The SPS samples also exhibited superconducting critical current density at 77 K, Jc(77K), between 2 and 10 A/cm2, values much smaller than ∼ 22 A/cm2 measured in the reference sample. Reoxygenation of the SPS samples, post-annealed in air at different temperatures and times, was found to improve their microstructural and transport properties. Besides the suppression of the Bragg peaks belonging to the Bi-2212 phase, the superconducting properties of the post-annealed samples and particularly Jc(77K) were comparable or better than those corresponding to the reference sample. Post-annealed samples at 750 °C for 5 min exhibited Jc(77K) ∼130 A/cm2 even when uniaxially pressed at only 50 MPa.
Nanostructured thermoelectric cobalt oxide by exfoliation/restacking route
Authors: Kim Jong-Young , Kim Jin-Il , Choi Soon-Mok , Soo Lim Young , Seo Won-Seon , Jin Hwang Hae
Published: December 2012

We report on enhanced thermoelectric (TE) properties of two-dimensional (2D)-nanostructured cobalt oxides prepared by the exfoliation/restacking method. Polycrystalline [(NaxCoO2)/(CaO)n] (x = 0.48-0.58 and n = 0.14-0.23) were synthesized by restacking the exfoliated Na0.7CoO2 with CaCl2. The composite oxide of [(NaxCayCoO2)/(LizCoO2)m] (x = 1.8, y = 1.2, and z = 0.24; m = 5) was produced with a 2D-superlattice structure, in which the exfoliated NaxCoO2 and LizCoO2 nanolayers were alternately stacked. The substitution of Ca2+ for Na+ of the restacked compounds decreases the carrier density, which results in increases of Seebeck coefficient and resistivity. The doping of the restacked compounds was found to be comparable to that of NaxCoO2 (x > 0.85). Despite the decreased vacancy of interlayer cations, the present restacked compounds show reduced thermal conductivity compared to the pristine sample. Due to the decrease of in-plane thermal conductivity, figure of merit (ZT) values of the restacked compounds increase in comparison to that of the pristine samples, which shows the beneficial effect of the nanostructure on the thermoelectric property. According to the increasing amount of calcium during the restacking process, the carrier density decreased by lower hole doping, resulting in the increased in-plane Seebeck coefficients, however, the resulting ZT value remains between 0.3∼0.4 because of the increased thermal conductivity due to higher sintering temperature. It has been found that the cobalt oxide exfoliated by tetramethylammonium (TMA) exhibits more significantly reduced thermal conductivity than that by octylamine (OA), resulting in a larger ZT value. This result implies that the nanolayer of NaxCoO2 exfoliated by TMA is thinner than by OA, which results in more significant phonon scattering in two-dimensional CoO2 layer.