bluuebunny/crossref_metadata_2025 huggingface dataset:
Extraction of helium from individual interplanetary dust particles by step‐heating
Authors: Nier A. O. , Schlutter D. J.
Published: June 2012

Abstract Fragments from 20 individual particles, collected in the Earth's stratosphere and believed to be interplanetary dust particles (IDPs), were obtained from NASA's Johnson Space Center collection and subjected to step‐heating to see if differences in the release pattern for 4He could be observed which might provide clues to the origin of the particles. Comparisons were made to the release pattern for 18 individual lunar surface grains heated in the same manner. Twelve of the IDP fragments contained an appreciable amount of 4He, 50 percent of which was released by the time the particles were heated to approximately 630 °C. For the 18 individual lunar grains the corresponding average temperature was 660 °C. The 3He/4He ratios found for these fragments agreed well with those found for deep Pacific magnetic fines believed to be of extraterrestrial origin, and were comparable to those which have been observed for the solar wind and lunar surface soil grains. Four of the IDP fragments contained appreciably less 4He, and this was released at a higher temperature. The remaining four fragments had too little 4He to permit a determination. From Flynn's analyses of the problem of the heating of IDPs in their descent in the atmosphere, the present results suggest that the parent IDPs of the 12 particles which contained an appreciable amount of 4He suffered very little heating in their descent and are likely of asteroidal origin, although one cannot rule out the possibility that at least some of them had a cometary origin and entered the earth's atmosphere at a grazing angle. Mineralogical and morphological studies on fragments companion to those used in the present investigation are under way. When these are completed, a more definite picture should emerge.
On the thermal history of heavily shocked Yanzhuang H‐chondrite
Authors: Begemann F. , Palme H. , Spettel B. , Weber H. W.
Published: June 2012

Abstract Partly shock‐melted Yanzhuang H‐chondrite, now classified as petrological type H6 but before the shock event of type H4, was subjected to the shock‐heating 2.6 Ma ago at the time it was spalled off its parent body and came into being as a meteoroid of ca. 30 cm radius. At that time the unmelted portion of the meteoroid suffered an almost complete loss of its radiogenic 4He and 40Ar while the contents of the most volatile non‐noble gas elements Zn and Se were not measurably affected. The melted portion of Yanzhuang is also essentially void of radiogenic 4He (10 ± 4 × 10−8 cm3 STP/g) but it has retained some 80% of its radiogenic 40Ar, presumably because in the melt the increase of the diffusion length more than compensated the increase of the diffusion constant.
The Leonard Medal Address
Authors: Clayton Donald D.
Published: June 2012

Abstract— The science of nucleosynthesis was substantially inspired by chemical analyses of meteorites. As if in repayment, that theory now imbues meteoritics with enlarged meaning. I recount the emergence of four great issues for nucleosynthesis—issues that received decades of my own attention; and I describe unexpected abundance patterns within meteorites that were suggested by the resolution of those issues. The latter have altered the information content of meteoritic science. The issues are:

1. a quantitative s‐process theory

2. cosmoradiogenic chronology

3. explosive nucleosynthesis and gamma‐ray astronomy

4. cosmic chemical memory

Starting from historical origins for each issue, I comment upon both the broad cultural canvas in which they lie and my own work in their establishment. Examples of predicted (or rationalized) meteoritic measurements illustrate our surprised delight at the expansion of the range and power of meteoritic science.
Tabbita: An L6c chondrite from New South Wales, Australia
Authors: Bevan A. W. R. , Griffin B. , Pogson R. E. , Sutherland F. L.
Published: June 2012

Abstract— A crusted stone weighing 3.10 kg was found in 1983 near Tabbita in south central New South Wales (ca. 34°03′S, 145°50′E), Australia. Compositions of the ferro‐magnesian silicates (olivine Fa24.6; orthopyroxene Fs20.9) show that the meteorite belongs to the L‐group of chondrites. Uniformity of silicate compositions and the presence of abundant crystalline plagioclase feldspar (An10.8Ab81.7Or7.5) show that the meteorite belongs to petrologic type 6. Silicates that display undulose extinction, and the absence of any thermal effects induced by shock indicate that Tabbita is shock facies c. Tabbita is distinct from several other L6 chondrites found in the same general area.
An analysis of differential impact melt‐crater scaling and implications for the terrestrial impact record
Authors: Grieve R. A. F. , Cintala M. J.
Published: June 2012

Abstract— It has been known for some time that the volume of impact melt (Vm) relative to that of the transient cavity (Vtc) increases with the magnitude of the impact event. This paper investigates the influence that this phenomenon has on the nature of terrestrial impact craters. A model of impact melting is used to estimate the volume of melt produced during the impact of chondritic projectiles into granite targets at velocities of 15, 25, and 50 km S−1. The dimensions of transient cavities formed under the same impact conditions are calculated from current crater‐scaling relationships, which are derived from dimensional analysis of data from cratering experiments. Observed melt volumes at terrestrial craters are collated from the literature and are paired with the transient‐cavity diameters (Dtc) of their respective craters; these diameters were determined through an established empirical relationship. The model and observed melt volumes have very similar trends with increasing transient‐cavity diameter. This Vm‐Dtc relationship is then used to make predictions regarding the nature of the terrestrial cratering record. In particular, with increasing size of the impact event, the depth of melting approaches the depth of the transient cavity. As a consequence, the base of the cavity, which ultimately would appear as an uplifted central structure in a complex crater, will record shock stresses that will increase up to a maximum of partial melting. Examination of the terrestrial record indicates a general trend for higher recorded shock levels in central structures at larger diameters; impact structures in the 100‐km size range record partially melted and vesiculated parautochthonous target rocks in their centers. In addition, as the depth of melting approaches a depth equivalent to that attained by the base of the transient cavity, the floor of the transient cavity will have progressively less strength, with the result that cavity modification and uplift will not produce topographic central peaks. Again, the observed terrestrial record is not inconsistent with this prediction, and we offer differential melt scaling as a possible mechanism for the transition from central topographic peaks to rings with increasing crater diameter. Among other implications is the likelihood that impact basins in the 1000‐km size range on the early Earth would not have the same multi‐ring form as observed on the moon.
The COMET experiment
Authors: Borg J. , Bibring J.‐P. , Langevin Y. , Salvetat Ph. , Vassent B.
Published: June 2012

Abstract— The COMET program is a program for the collection of micron to submicron interplanetary dust particles in low Earth orbits. Since collection takes place as the Earth crosses a given meteor stream, the particles are mainly of cometary origin. The grain remnants, located at their impact positions on high purity metallic collectors, are analysed in the laboratory for chemical and isotopical identification. The COMET‐1 experiment took place in 1985 October, during encounter with the Draconid meteor stream, related to the Giacobini‐Zinner comet. The fluence of extraterrestrial grains that had impacted our detectors was ∼10x higher than the value of the mean meteroid fluence at ∼1AU, which suggests that most of the grains originated from the Giacobini‐Zinner comet. One of the most important results of their chemical analysis was that ∼90% of them are enriched in low Z elements (C and O have undoubedly been identified). They could contain a CHON phase similar to that observed in the close environment of Halley's nucleus. The first imagery of the grain remnants by field emission scanning electron microscopy suggests that they are very low density aggregates still present at the impacting positions which, in most cases, are very different from the impact craters observed for the same mean relative velocity for full grains of the same size. These results show that the COMET program has constituted an important step towards the analysis of cometary material and the understanding of the evolution of the early Solar System.
The natural thermoluminescence of meteorites VI: Carbon‐14, thermoluminescence and the terrestrial ages of meteorites
Authors: Benoit P. H. , Jull A. J. T. , McKeever S. W. S. , Sears D. W. G.
Published: June 2012

Abstract Research on meteorite finds, especially those from the Antarctic and from desert regions in Australia, Africa, and America, has become increasingly important, notably in studies of possible changes in the nature of the meteorite flux in the past. One important piece of information needed in the study of such meteorites is their terrestrial age which can be determined using a variety of methods, including 14C, 36Cl, and 81Kr. Natural thermoluminescence (TL) levels in meteorites can also be used as an indicator of terrestrial age. In this paper, we compare 14C‐determined terrestrial ages with natural TL levels in finds from the Prairie States (central United States), a group of finds from Roosevelt County (New Mexico, USA), and a group from the Sahara Desert. We find that, in general, the natural TL data are compatible with the 14C‐derived terrestrial ages using a 20 °C TL decay curve for the Prairie States and Roosevelt County and a 30 °C decay curve for the Saharan meteorites. We also present TL data for a group of meteorites from the Sahara desert which has not been studied using cosmogenic radionuclides. Within these data there are distinct terrestrial age clusters which probably reflect changes in meteorite preservation efficiency over ∼ 15, 000 years in the region.
Floor‐fractured crater models of the Sudbury Structure, Canada: Implications for initial crater size and crater modification
Authors: Wichman R. W. , Schultz P. H.
Published: June 2012

Abstract The pattern of radial and concentric offset dikes at Sudbury strongly resembles fracture patterns in certain volcanically modified craters on the Moon. Since the Sudbury dikes apparently formed shortly after the impact event, this resemblance suggests that early endogenic modification at Sudbury was comparable to deformation in lunar floor‐fractured craters. Although regional deformation has obscured many details of the Sudbury Structure, such a comparison of Sudbury with lunar floor‐fractured craters provides two alternative models for the original size and surface structures of the Sudbury basin. First, the Sudbury date pattern can be correlated with fractures in the central peak crater Haldane (36 km in diameter). This comparison indicates an initial Sudbury diameter of between 100 and 140 km but requires loss of a central peak complex for which there is little evidence. Alternatively, comparison of the Sudbury dikes with fractures in the two‐ring basin Schrödinger indicates an initial Sudbury diameter of at least ∼ 180 km, which is in agreement with other recent estimates for the size of the Sudbury Structure. In addition to constraining the size and structure of the original Sudbury crater, these comparisons also suggest that crater modification may reflect different deformation mechanisms at different sizes. Most lunar floor‐fractured craters are attributed to deformation over a shallow, crater‐centered intrusion; however, there is no evidence for such an intrusion at Sudbury. Instead, melts from the evolving impact melt sheet probably entered fractures formed by isostatically‐induced flexure of the crater floor. Since most of the lunar floor‐fractured craters are too small (<100‐km diameter) to induce significant isostatic adjustment, crater modification by isostatic uplift apparently is limited to only the largest of craters, whereas deformation over igneous intrusions dominates the modification of smaller craters.
Apollo 12 ropy glasses revisited
Authors: Wentworth S. J. , McKay D. S. , Lindstrom D. J. , Basu A. , Martinez R. R. , Bogard D. D. , Garrison D. H.
Published: June 2012

Abstract— We analyzed ropy glasses from Apollo 12 soils 12032 and 12033 by a variety of techniques including SEM/EDX, electron microprobe analysis, INAA, and 39Ar‐40Ar age dating. The ropy glasses have KREEP‐like compositions different from those of local Apollo 12 mare soils; it is likely that the ropy glasses are of exotic origin. Mixing calculations indicate that the ropy glasses formed from a liquid enriched in KREEP and that the ropy glass liquid also contained a significant amount of mare material. The presence of solar Ar and a trace of regolith‐derived glass within the ropy glasses are evidence that the ropy glasses contain a small regolith component Anorthosite and crystalline breccia (KREEP) clasts occur in some ropy glasses. We also found within these glasses clasts of felsite (fine‐grained granitic fragments) very similar in texture and composition to the larger Apollo 12 felsites, which have a 39Ar‐40Ar degassing age of 800 ± 15 Ma (Bogard et al, 1992). Measurements of 39Ar‐40Ar in 12032 ropy glass indicate that it was degassed at the same time as the large felsite although the ropy glass was not completely degassed. The ropy glasses and felsites, therefore, probably came from the same source. Most early investigators suggested that the Apollo 12 ropy glasses were part of the ejecta deposited at the Apollo 12 site from the Copernicus impact Our new data reinforce this model. If these ropy glasses are from Copernicus, they provide new clues to the nature of the target material at the Copernicus she, a part of the Moon that has not been sampled directly.
ALH84001, a cumulate orthopyroxenite member of the martian meteorite clan
Authors: Mittlefehldt David W.
Published: June 2012

Abstract— ALH84001, originally classified as a diogenite, is a coarse‐grained, cataclastic, orthopyroxenite meteorite related to the martian (SNC) meteorites. The orthopyroxene is relatively uniform in composition, with a mean composition of Wo3.3En69.4Fs27.3. Minor phases are euhedral to subhedral chromite and interstitial maskelynite, An31.1Ab63.2Or5.7, with accessory augite, Wo42.2En45.1Fs12.7, apatite, pyrite and carbonates, Cc11.5Mg58.0Sd29.4Rd1.1. The pyroxenes and chromites in ALH84001 are similar in composition to these phases in EETA79001 lithology A megacrysts but are more homogeneous. Maskelynite is similar in composition to feldspars in the nakhlites and Chassigny. Two generations of carbonates are present, early (pre‐shock) strongly zoned carbonates and late (post‐shock) carbonates. The high Ca content of both types of carbonates indicates that they were formed at moderately high temperature, possibly ∼700 °C. ALH84001 has a slightly LREE‐depleted pattern with La 0.67x and Lu 1.85x CI abundances and with a negative Eu anomaly (Eu/Sm 0.56x CI). The uniform pyroxene composition is unusual for martian meteorites, and suggests that ALH84001 cooled more slowly than did the shergottites, nakhlites or Chassigny. The nearly monomineralic composition, coarse‐grain size, homogenous orthopyroxene and chromite compositions, the interstitial maskelynite and apatite, and the REE pattern suggest that ALH84001 is a cumulate orthopyroxenite containing minor trapped, intercumulus material.
Shocked lithologies at the Wanapitei impact structure, Ontario, Canada
Authors: Grieve R. A. F. , Ber T. J.
Published: June 2012

Abstract The ∼7.5 km diameter Wanapitei impact structure (46°45′N; 80°45′W) lies entirely within Lake Wanapitei in central Ontario, Canada. Impact lithologies are known only from glacial float at the southern end of the lake. Over 50% of the impact lithologies recovered from this float can be classified as suevite, <20% as highly shocked and partially melted arkosic metasediments of the target rock Mississagi Formation or, possibly, the Serpent Formation and <20% as glassy impact melt rocks. An additional <5% of the samples have similarities to the suevite but have up to 50% glass clasts and are tentatively interpreted as fall‐back material. The glassy impact melt rocks fall into two textural and mineralogical types: a perlitically fractured, colorless glass matrix variant, with microlites of hypersthene with up to 11.5% Al2O3 and a “felted” matrix variant, with evidence of flow prior to the crystallization of tabular orthopyroxene. These melt glasses show chemical inhomogeneities on a microscopic scale, with areas of essentially SiO2, even when appearing optically homogeneous. They are similar in bulk composition for major elements, but the felted matrix variant is ∼5×more enriched in Ni, Co and Cr, the interelement ratios of which are indicative of an admixture of a chondritic projectile. Mixing models suggest that the glassy impact melt rocks can be made from the target rocks in the proportions: ∼55% Gowganda wacke, ∼42% Serpent arkose and ∼3% Nipissing intrusives. Geologic reconstructions suggest that this is a reasonable mixture of potential target rocks at the time of impact.
Collisional records in LL‐chondrites
Authors: Graf Thomas , Marti Kurt
Published: June 2012

Abstract One‐third of all the LL‐chondrites have exposure ages of ∼15 Ma and were exposed to cosmic rays following a collisional break‐up. The probability that the 15‐Ma peak represents a random signal is calculated to be less than 2%. Considerably lower probabilities are obtained if only LL5s or subgroups of high 40Ar retention are used. Furthermore, we show that the peak shape agrees with statistical constraints obtained from multiple analyses of samples from the St. Severin LL6‐chondrite. The frequency in and out of the 15‐Ma peak varies significantly for different petrographic LL‐types. The radiogenic 40Ar retention systematics (most LL‐chondrites retained 40Arrad) shows that no substantial heat pulse resulted in the 15‐Ma collisional event. Interestingly, smaller exposure age clusters at ∼28 Ma and ∼40 Ma match up well with clusters in the histogram of L‐chondrites. The distribution of LL‐exposure ages is not consistent with that expected for a quasi‐continuous injection of LL material into a resonance zone of the asteroid belt. The near absence of exposure ages shorter than 8 Ma either indicates a lack of recent collisional events or considerably longer transfer times than inferred from dynamical considerations.
A carbon‐14 depth profile in the L5 chondrite Knyahinya
Authors: Jull A. J. T. , Donahue D. J. , Reedy R. C. , Masarik J.
Published: June 2012

Abstract We report on a series of measurements of 14C in samples of the L‐chondrite Knyahinya, as a function of depth. The results show 14C concentrations ranging from 37 to 58 dpm/kg. These measurements are compared to the levels of 21Ne, 10Be and noble‐gas ratios in this meteorite reported by Graf et al (1990). We also compare the 14C data to the expected profile based on two sets of model calculations. The behavior of this radioisotope with depth is similar to that expected from the models, and good agreement with the profiles of other nuclides is also observed.
Glass‐rich chondrules in ordinary chondrites
Authors: Krot Alexander N. , Rubin Alan E.
Published: June 2012

Abstract There are two types of glass‐rich chondrules in unequilibrated ordinary chondrites (OC): (1) porphyritic chondrules containing 55–85 vol% glass or microcrystalline mesostasis and (2) nonporphyritic chondrules, containing 90–99 vol% glass. These two types are similar in mineralogy and bulk composition to previously described Al‐rich chondrules in OC. In addition to Si‐, Al‐ and Na‐rich glass or Ca‐Al‐rich microcrystalline mesostasis, glass‐rich chondrules contain dendritic and skeletal crystals of olivine, Al2O3‐rich low‐Ca pyroxene and fassaite. Some chondrules contain relict grains of forsterite ± Mg‐Al spinel. We suggest that glass‐rich chondrules were formed early in nebular history by melting fine‐grained precursor materials rich in refractory (Ca, Al, Ti) and moderately volatile (Na, K) components (possibly related to Ca‐Al‐rich inclusions) admixed with coarse relict forsterite and spinel grains derived from previously disrupted type‐I chondrules.
Suevite breccia from the Ries crater, Germany: Origin, cooling history and devitrification of impact glasses
Authors: Engelhardt W. V. , Arndt J. , Fecker B. , Pankau H. G.
Published: June 2012

Abstract— The distribution and petrography of surficial suevite breccias of the Ries impact crater in Southern Germany are reviewed, and the morphology, petrography and chemical composition of impact glasses in suevite breccias and their postdepositional devitrification is synthesized. Origin and thermal history of suevite breccia and suevite glasses are inferred from these data and from recent results of cooling and crystallization experiments with suevite glass melts under controlled conditions. In a montmorillonitic groundmass, the suevite breccia contains pieces of glass, up to some decimeters in size, and crystalline rock clasts of all stages of shock metamorphism. The glass particles originated in impact melt of basement gneisses and cooled by adiabatic pressure release from ∼80 GPa to atmospheric pressure during ejection from the crater. They were deposited on the ground together with the other suevite components at a temperature of ∼750 °C. Fractured glass pieces in the breccia show that during deposition of the suevite the temperature was below the temperature at which undercooled melt transforms to rigid glass. The suevite cooled after deposition mainly by convection of heat by emanating gases and vapors. In chilled layers at the base and at the top of suevite deposits, the glasses are preserved in vitreous state. Between these zones, the glasses were devitrified, yet crystallization of pyroxene, plagioclase and magnetite took place below the glass‐transformation temperature. Annealing experiments show that this unusual devitrification below the transformation temperature can be explained by the impact origin of suevite glasses. Due to rapid adiabatic cooling on decompression, the glasses were oversaturated with water and internally strained. Under these conditions, devitrification, especially the formation of plagioclase, was possible at temperatures below the transformation range. The origin from adiabatically cooled impact melt of deep‐seated rocks distinguishes water‐bearing suevite glasses from the Ries‐derived, water‐free moldavite tektites, which are interpreted as condensates of vaporized, surficial sediments (Engelhardt et al., 1987).
A petrographic history of martian meteorite ALH84001: Two shocks and an ancient age
Authors: Treiman Allan H.
Published: June 2012

Abstract— ALH84001 is an igneous meteorite, an orthopyroxenite of martian origin. It contains petrographic evidence of two shock metamorphic events, separated by thermal and chemical events. The evidence for two shock events suggests that ALH84001 is ancient and perhaps a sample of the martian highlands. From petrography and mineral chemistry, the history of ALH84001 must include: crystallization from magma, a first shock (impact) metamorphism, thermal metamorphism, low‐temperature chemical alteration, and a second shock (impact) metamorphism. Originally, ALH84001 was igneous, an orthopyroxene‐chromite cumulate. In the first shock event, the igneous rock was cut by melt‐breccia or cataclastic veinlets, now bands of equigranular fine‐grained pyroxene and other minerals (crush zones). Intact fragments of the cumulate were fractured and strained (now converted to polygonized zones). The subsequent thermal metamorphism (possibly related to the first shock) annealed the melt‐breccia or cataclastic veinlets to their present granoblastic texture and permitted chemical homogenization of all mineral species present. The temperature of metamorphism was at least 875 °C, based on mineral thermometers. Next, Mg‐Fe‐Ca carbonates and pyrite replaced plagioclase in both clasts and granular bands, producing ellipsoidal carbonate globules with sub‐micron scale compositional stratigraphy, repeated identically in all globules. The second shock event produced microfault offsets of carbonate stratigraphy and other mineral contacts, radial fractures around chromite and maskelynite, and strain birefringence in pyroxene. Maskelynite could not have been preserved from the first shock event, because it would have crystallized back to plagioclase. The martian source area for ALH84001 must permit this complex, multiple impact history. Very few craters on young igneous surfaces are on or near earlier impact features. It is more likely that ALH84001 was ejected from an old igneous unit (Hesperian or Noachian age), pocked by numerous impact craters over its long exposure at the martian surface.
Boron cosmochemistry. Part II: Boron nucleosynthesis and condensation temperature
Authors: Zhai Mingzhe
Published: June 2012

Abstract— The new B solar‐system abundance calculated by Zhai and Shaw (1994), 16.9 atoms/106 Si (or 606 atoms/1012 H) is used to reevaluate the different possibilities of LiBeB (except 7Li) nucleosynthesis. The revised abundances support two models: (1) Light elements were formed by continual bombardment of interstellar medium (ISM) by galactic cosmic rays (GCRs), but these galactic cosmic rays should contain a very intense low‐energy component, in the form of E−5 which cannot be observed near the Earth due to solar modulation effects; (2) Light elements are a mixture of two sources. In the first source, light elements were synthesized by continual bombardment of interstellar medium by galactic cosmic rays. In the second source, they were made by the interactions of C and O nuclei ejected from supernovae with the H and He in the surrounding gas. The first source constitutes ∼46% of total B.

The Si‐normalized and CI‐meteorite‐normalized abundances of common and volatile elements in carbonaceous chondrites show a linear correlation with their condensation temperatures. Using this relationship and the normalized B abundances in CM, CO, and CV meteorites, we can estimate the B condensation temperature to be ∼910 K, which is similar to Ga.
Meteorites from the Sahara: Find locations, shock classification, degree of weathering and pairing
Authors: Bischoff A. , Geiger T.
Published: June 2012

Abstract— The Sahara is an extraordinary area for recovering meteorites. Between 1989 and 1993, 471 meteorites were collected in Algeria and Libya. Studies of 465 samples have been done. In addition to the classifications of the meteorites that were published in various “Meteoritical Bulletins” in past years, we present here the results on the determination of the shock metamorphism and the degree of weathering. Also, we have tried to solve the pairing problem by considering the find locations, the degree of shock metamorphism, the degree of weathering, and the mineral compositions of olivine and pyroxene. A comprehensive table listing all samples contains references about previous work on these meteorites.
Temporal and Convective Inertia Effects in Plain Journal Bearings With Eccentricity, Velocity and Acceleration
Authors: Dousti Saeid , Cao Jianming , Younan Amir , Allaire Paul , Dimond Tim
Published: June 2012

This paper extends the theory originally developed by Tichy (Tichy and Bou-Said, 1991, Hydrodynamic Lubrication and Bearing Behavior With Impulsive Loads,” STLE Tribol. Trans. 34, pp. 505–512) for impulsive loads to high reduced Reynolds number lubrication. The incompressible continuity equation and Navier-Stokes equations, including inertia terms, are simplified using an averaged velocity approach to obtain an extended form of short bearing Reynolds equation which applies to both laminar and turbulent flows. A full kinematic analysis of the short journal bearing is developed. Pressure profiles and linearized stiffness, damping and mass coefficients are calculated for different operating conditions. A time transient solution is developed. The change in the rotor displacements when subjected to unbalance forces is explored. Several comparisons between conventional Reynolds equation solutions and the extended Reynolds number form with temporal inertia effects are presented and discussed. In the specific cases considered in this paper, the primary conclusion is that the turbulence effects are significantly more important than inertia effects.
Rapid Progression of Ocean Acidification in the California Current System
Authors: Gruber Nicolas , Hauri Claudine , Lachkar Zouhair , Loher Damian , Frölicher Thomas L. , Plattner Gian-Kasper
Published: June 2012

Acidification Blues

The increase in the concentration of atmospheric carbon dioxide threatens the health of the ocean's ecosystems because of the resulting acidification of the ocean and the decrease in its carbonate saturation state.

Gruber
et al.

(p.
220
, published online 14 June) used a regional ocean model to project how the saturation state of aragonite, a form of calcium carbonate that is produced by many marine organisms, will change in the California Current System through the year 2050. The sea floor along many parts of the California coast is likely to become exposed to year-round aragonite undersaturation within the next 20 to 30 years, a situation that could severely reduce the range of habitats for marine shellfish.
Function, Targets, and Evolution of
Caenorhabditis elegans
piRNAs
Authors: Bagijn Marloes P. , Goldstein Leonard D. , Sapetschnig Alexandra , Weick Eva-Maria , Bouasker Samir , Lehrbach Nicolas J. , Simard Martin J. , Miska Eric A.
Published: June 2012

Secondary Endogenous Small and Interfering

In many eukaryotes, Piwi proteins bind small noncoding Piwi-interacting RNAs (piRNAs) that function to silence transposons in the germ line and protect the germ line from transposable element–driven recombination and mutation.

Bagijn
et al.

(p.
574
, published online 14 June; see the Perspective by

Xiol and Pillai

) show that in the nematode,
Caenorhabditis elegans
, a messenger RNA (mRNA) that contains a piRNA target sequence gives rise to a second, downstream class of small RNAs known as secondary endogenous small interfering RNAs, or endo siRNAs. These endo siRNAs map to the vicinity of the piRNA complementary sequence in the mRNA target and depend on both Piwi and on factors involved in the related RNA interference pathway for their genesis, but not on the Piwi slicer activity. Mapping the endo siRNAs reveals that piRNAs can target imperfectly matched targets and that piRNAs target a subset of both transposons and endogenous genes for silencing.
Message in an Exosome
Authors: Wong Wei
Published: June 2012

Melanomas transfer various proteins, including the receptor MET, to bone marrow–derived cells through exosomes to promote metastasis.
Emergence of Metallo-β-Lactamase GIM-1 in a Clinical Isolate of Serratia marcescens
Authors: Rieber Heime , Frontzek Andre , Pfeifer Yvonne
Published: June 2012

The metallo-β-lactamase GIM-1 (German imipenemase) has been found so far only in clinical isolates of
Pseudomonas aeruginosa
from Germany. Here we report the detection of
bla
GIM-1
in a clinical strain of
Serratia marcescens
that was isolated from urine, blood, and wound samples over a period of 20 months. The strain was repeatedly isolated from one patient in two German hospitals and an outpatient department located in the region in which all previously described GIM-1-producing
P. aeruginosa
strains were identified.
Broadening the Spectrum of β-Lactam Antibiotics through Inhibition of Signal Peptidase Type I
Authors: Therien Alex G. , Huber Joann L. , Wilson Kenneth E. , Beaulieu Patrick , Caron Alexandre , Claveau David , Deschamps Kathleen , Donald Robert G. K. , Galgoci Andrew M. , Gallant Michel , Gu Xin , Kevin Nancy J. , Lafleur Josiane , Leavitt Penny S. , Lebeau-Jacob Christian , Lee Suzy S. , Lin Molly M. , Michels Anna A. , Ogawa Aimie M. , Painter Ronald E. , Parish Craig A. , Park Young-Whan , Benton-Perdomo Liliana , Petcu Mihai , Phillips John W. , Powles Mary Ann , Skorey Kathryn I. , Tam John , Tan Christopher M. , Young Katherine , Wong Simon , Waddell Sherman T. , Miesel Lynn
Published: June 2012

The resistance of methicillin-resistant
Staphylococcus aureus
(MRSA) to all β-lactam classes limits treatment options for serious infections involving this organism. Our goal is to discover new agents that restore the activity of β-lactams against MRSA, an approach that has led to the discovery of two classes of natural product antibiotics, a cyclic depsipeptide (krisynomycin) and a lipoglycopeptide (actinocarbasin), which potentiate the activity of imipenem against MRSA strain COL. We report here that these imipenem synergists are inhibitors of the bacterial type I signal peptidase SpsB, a serine protease that is required for the secretion of proteins that are exported through the Sec and Tat systems. A synthetic derivative of actinocarbasin, M131, synergized with imipenem both
in vitro
and
in vivo
with potent efficacy. The
in vitro
activity of M131 extends to clinical isolates of MRSA but not to a methicillin-sensitive strain. Synergy is restricted to β-lactam antibiotics and is not observed with other antibiotic classes. We propose that the SpsB inhibitors synergize with β-lactams by preventing the signal peptidase-mediated secretion of proteins required for β-lactam resistance. Combinations of SpsB inhibitors and β-lactams may expand the utility of these widely prescribed antibiotics to treat MRSA infections, analogous to β-lactamase inhibitors which restored the utility of this antibiotic class for the treatment of resistant Gram-negative infections.
Social inequality and infant health in the UK: systematic review and meta-analyses
Authors: Weightman Alison L , Morgan Helen E , Shepherd Michael A , Kitcher Hilary , Roberts Chris , Dunstan Frank D
Published: June 2012

Objectives

To determine the association between area and individual measures of social disadvantage and infant health in the UK.

Design

Systematic review and meta-analyses.

Data sources

26 databases and websites, reference lists, experts in the field and hand-searching.

Study selection

36 prospective and retrospective observational studies with socioeconomic data and health outcomes for infants in the UK, published from 1994 to May 2011.

Data extraction and synthesis

2 independent reviewers assessed the methodological quality of the studies and abstracted data. Where possible, study outcomes were reported as ORs for the highest versus the lowest deprivation quintile.

Results

In relation to the highest versus lowest area deprivation quintiles, the odds of adverse birth outcomes were 1.81 (95% CI 1.71 to 1.92) for low birth weight, 1.67 (95% CI 1.42 to 1.96) for premature birth and 1.54 (95% CI 1.39 to 1.72) for stillbirth. For infant mortality rates, the ORs were 1.72 (95% CI 1.37 to 2.15) overall, 1.61 (95% CI 1.08 to 2.39) for neonatal and 2.31 (95% CI 2.03 to 2.64) for post-neonatal mortality. For lowest versus highest social class, the odds were 1.79 (95% CI 1.43 to 2.24) for low birth weight, 1.52 (95% CI 1.44 to 1.61) for overall infant mortality, 1.42 (95% CI 1.33 to1.51) for neonatal and 1.69 (95% CI 1.53 to 1.87) for post-neonatal mortality. There are similar patterns for other infant health outcomes with the possible exception of failure to thrive, where there is no clear association.

Conclusions

This review quantifies the influence of social disadvantage on infant outcomes in the UK. The magnitude of effect is similar across a range of area and individual deprivation measures and birth and mortality outcomes. Further research should explore the factors that are more proximal to mothers and infants, to help throw light on the most appropriate times to provide support and the form(s) that this support should take.
MAGNETIZATION PLATEAU AND THE MINIMAL MODEL OF A SPIN INTERACTIVE SYSTEM
Authors: BAI ZHAN WU , CHEN ZHOU FEI
Published: June 2012

We demonstrate using two examples that a minimal model of a spin system can present qualitative correct magnetization plateaus which are almost the same as the original model. Some arguments on the generality of the minimal model approach are given. The approach can serve as a primary approximation and a assistance to the analytical and numerical methods.
TIME INTERVAL AND LATTICE VIBRATION IN RAMAN EFFECT, PHOTOELECTRIC EFFECT AND PLANE MIRROR REFLECTION
Authors: KUMAR M. , SAHOO S.
Published: June 2012

Time interval between the incident and scattered photon in Raman effect and absorption of photon and emission of electron in photoelectric effect has not been determined till now. This is because there is no such high level instrument discovered till now to detect time interval to such a small level. But this can be calculated theoretically by applying a basic principle of physics like impulse is equal to the change in momentum. Considering the collision between electron and photon as perfect inelastic collision in photoelectric effect, elastic and inelastic collision in Raman effect and elastic collision in plane mirror reflection and the interaction between electron and photon as strong gravitational interaction, we calculate the required time interval. During these phenomena, there is lattice vibration which can be quantized as phonon particles.
THE TERM STRUCTURE OF IMPLIED VOLATILITY IN SYMMETRIC MODELS WITH APPLICATIONS TO HESTON
Authors: DE MARCO S. , MARTINI C.
Published: June 2012

We study the term structure of the implied volatility in the presence of a symmetric smile. Exploiting the result by Tehranchi (2009) that a symmetric smile generated by a continuous martingale necessarily comes from a mixture of normal distributions, we derive representation formulae for the at-the-money (ATM) implied volatility level and curvature in a general symmetric model. As a result, the ATM curve is directly related to the Laplace transform of the realized variance. The representation formulae for the implied volatility and its curvature take semi-closed form as soon as this Laplace transform is known explicitly. To deal with the rest of the volatility surface, we build a time dependent SVI-type (Gatheral, 2004) model which matches the ATM and extreme moneyness structure. As an instance of a symmetric model, we consider uncorrelated Heston: in this framework, the SVI approximation displays considerable performances in a wide range of maturities and strikes. All these results can be applied to skewed smiles by considering a displaced model. Finally, a noteworthy fact is that all along the paper we avoid dealing with any complex-valued function.
SOCIAL DYNAMICS AND COOPERATION: THE CASE OF NONHUMAN PRIMATES AND ITS IMPLICATIONS FOR HUMAN BEHAVIOR
Authors: CRONIN KATHERINE A. , SÁNCHEZ ANGEL
Published: June 2012

The social factors that influence cooperation have remained largely uninvestigated but have the potential to explain much of the variation in cooperative behavior observed in the natural world. We show here that certain dimensions of the social environment, namely the size of the social group, the degree of social tolerance expressed, the structure of the dominance hierarchy, and the patterns of dispersal, may influence the emergence and stability of cooperation in predictable ways. Furthermore, the social environment experienced by a species over evolutionary time will have shaped their cognition to provide certain strengths and strategies that are beneficial in their species' social world. These cognitive adaptations will in turn impact the likelihood of cooperating in a given social environment. Experiments with one primate species, the cottontop tamarin, illustrate how social dynamics may influence emergence and stability of cooperative behavior in this species. We then take a more general viewpoint and argue that the hypotheses presented here require further experimental work and the addition of quantitative modeling to obtain a better understanding of how social dynamics influence the emergence and stability of cooperative behavior in complex systems. We conclude by pointing out subsequent specific directions for models and experiments that will allow relevant advances in the understanding of the emergence of cooperation.
THE TOPOLOGICAL STUDY OF IPR FULLERENES BY SZEGED AND REVISED SZEGED INDICES
Authors: MEHRANIAN Z. , MOTTAGHI A. , ASHRAFI A. R.
Published: June 2012

In this paper the Szeged and revised Szeged indices of an infinite family of IPR fullerenes with 50 + 10n carbon atoms and D 5h point group symmetry are computed. It seems that some chemico-physical properties of these fullerenes are derived from the mentioned topological invariants.
NASCENT ENTREPRENEURS AND THE TRANSITION TO ENTREPRENEURSHIP: WHY DO PEOPLE START NEW BUSINESSES?
Authors: ZANAKIS STELIOS H. , RENKO MAIJA , BULLOUGH AMANDA
Published: June 2012

What makes nascent entrepreneurs get their businesses up and running? We answer this by examining in a broad and unifying way: motivation and cognition, knowledge and experience and social support. We apply extensive multivariate analyses to a sample of 338 nascent entrepreneurs from the PSED database. Interestingly, most of our long-term (4½-year) model predictions of startup transition based on early antecedents are more accurate than the short-term ones — a practical strength of these models. Findings indicate that experienced, persistent, confident individuals, motivated mostly by non-financial outcomes, perceiving support from their social contacts and institutional environment, are likely to make the transition to a successful business.
CONJUGATE GRAPHS OF FINITE GROUPS
Authors: ERFANIAN A. , TOLUE B.
Published: June 2012

In this paper we introduce the conjugate graph [Formula: see text] associated to a nonabelian group G with vertex set G\Z(G) such that two distinct vertices join by an edge if they are conjugate. We show if [Formula: see text], where S is a finite nonabelian simple group which satisfy Thompson's conjecture, then G ≅ S. Further, if central factors of two nonabelian groups H and G are isomorphic and |Z(G)| = |Z(H)|, then H and G have isomorphic conjugate graphs.
A vocabulary of program slicing-based techniques
Authors: Silva Josep
Published: June 2012

This article surveys previous work on program slicing-based techniques. For each technique, we describe its features, its main applications, and a common example of slicing using such a technique. After discussing each technique separately, all of them are compared in order to clarify and establish the relations between them. This comparison gives rise to a classification of techniques which can help to guide future research directions in this field.
Recent thermal management techniques for microprocessors
Authors: Kong Joonho , Chung Sung Woo , Skadron Kevin
Published: June 2012

Microprocessor design has recently encountered many constraints such as power, energy, reliability, and temperature. Among these challenging issues, temperature-related issues have become especially important within the past several years. We summarize recent thermal management techniques for microprocessors, focusing on those that affect or rely on the microarchitecture. We categorize thermal management techniques into six main categories: temperature monitoring, microarchitectural techniques, floorplanning, OS/compiler techniques, liquid cooling techniques, and thermal reliability/security. Temperature monitoring, a requirement for Dynamic Thermal Management (DTM), includes temperature estimation and sensor placement techniques for accurate temperature measurement or estimation. Microarchitectural techniques include both static and dynamic thermal management techniques that control hardware structures. Floorplanning covers a range of thermal-aware floorplanning techniques for 2D and 3D microprocessors. OS/compiler techniques include thermal-aware task scheduling and instruction scheduling techniques. Liquid cooling techniques are higher-capacity alternatives to conventional air cooling techniques. Thermal reliability/security issues cover temperature-dependent reliability modeling, Dynamic Reliability Management (DRM), and malicious codes that specifically cause overheating. Temperature-related issues will only become more challenging as process technology continues to evolve and transistor densities scale up faster than power per transistor scales down. The overall objective of this survey is to give microprocessor designers a broad perspective on various aspects of designing thermal-aware microprocessors and to guide future thermal management studies.
Behavioral interface specification languages
Authors: Hatcliff John , Leavens Gary T. , Leino K. Rustan M. , Müller Peter , Parkinson Matthew
Published: June 2012

Behavioral interface specification languages provide formal code-level annotations, such as preconditions, postconditions, invariants, and assertions that allow programmers to express the intended behavior of program modules. Such specifications are useful for precisely documenting program behavior, for guiding implementation, and for facilitating agreement between teams of programmers in modular development of software. When used in conjunction with automated analysis and program verification tools, such specifications can support detection of common code vulnerabilities, capture of light-weight application-specific semantic properties, generation of test cases and test oracles, and full formal program verification. This article surveys behavioral interface specification languages with a focus toward automatic program verification and with a view towards aiding the Verified Software Initiative—a fifteen-year, cooperative, international project directed at the scientific challenges of large-scale software verification.
Evaluating the effectiveness of orientation indicators with an awareness of individual differences
Authors: Ziemek Tina , Creem-Regehr Sarah , Thompson William , Whitaker Ross
Published: June 2012

Understanding how users perceive 3D geometric objects can provide a basis for creating more effective tools for visualization in applications such as CAD or medical imaging. This article examines how orientation indicators affect users' accuracy in perceiving the shape of a 3D object shown as multiple views. Multiple views force users to infer the orientation of an object and recognize corresponding features between distinct vantage points. These are difficult tasks, and not all users are able to carry them out accurately. We use a cognitive experimental paradigm to evaluate the effectiveness of two types of orientation indicators on a person's ability to compare views of objects presented in different orientations. The orientation indicators implemented were colocated, which shared a center-point with the 3D object, or noncolocated with (displaced from) the 3D object. The study accounts for additional factors including object complexity, axis of rotation, and users' individual differences in spatial abilities. Our results show that an orientation indicator helps users in comparing multiple views, and that the effect is influenced by the type of aid, a person's spatial ability, and the difficulty of the task. In addition to establishing an effect of an orientation indicator, this article helps demonstrate the application of a particular experimental paradigm and analysis, as well as the importance of considering individual differences when designing interface aids.