Home About us Contact
|
Home About us Contact | ||
|
|
||
Composition Similar (composition + similar)
Selected AbstractsChemical variability of the leaf oil of 113 hybrids from Citrus clementina (Commun) × Citrus deliciosa (Willow Leaf)FLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2008Félix Tomi Abstract Essential oils of 113 Citrus clementina (Commun) × Citrus deliciosa (Willow Leaf) hybrids were obtained from leaves collected on trees located in the same orchard. Their chemical composition was investigated by capillary GC, GC,MS and 13C-NMR and the results were submitted to statistical analysis. Three chemical compositions were characterized. The crossing between clementine and mandarin produces mainly leaf oils characterized by a composition similar to those of the parents (sabinene/linalool or methyl N-methylanthranylate). However, several samples exhibited an original composition (,- terpinene/linalool). Copyright © 2008 John Wiley & Sons, Ltd. [source] Microfabric characteristics and rheological significance of ultra-high-pressure metamorphosed jadeite-quartzite and eclogite from Shuanghe, Dabie Mountains, ChinaJOURNAL OF METAMORPHIC GEOLOGY, Issue 2 2010L. WANG Abstract Quantitative analysis of the structural evolution of jadeite-quartzite, a rare ultra-high pressure (UHP) rock type from the Dabie Mountains of eastern China, sheds light on the formation and evolution of UHP orogenic belts worldwide. Geological mapping of the Shuanghe area, where jadeite-quartzites crop out, was carried out to determine the spatial relationships between different UHP rocks within this orogen. The deformation mechanisms of jadeite-quartzite, geodynamical parameters (stress, strain, strain rate), and microstructure including lattice preferred orientation (LPO) were determined from six jadeite-quartzite samples from the Shuanghe area. LPOs of clinopyroxene (jadeite and omphacite), garnet, rutile and quartz from these jadeite-quartzite samples are compared with those of three eclogites preserving different degrees of deformation from the Shuanghe area. Microstructural LPOs of jadeite, omphacite, garnet, rutile and quartz were determined using electron backscattered diffraction (EBSD) analysis. Quartz fabrics were largely recrystallized during late, low-grade stages of deformation, whereas garnet shows no strong LPO patterns. Rutile fabrics show a weak LS fabric along [001]. Jadeite and omphacite show the strongest eclogite facies LPO patterns, suggesting that they may provide important information about mantle deformation patterns and control the rheology of deeply subducted continental crust. Microstructural data show that the jadeite LPO patterns are similar to those of omphacite and vary between L- and S-types, which correlate with prolate and oblate grain shape fabrics (SPO); quartz LPOs are monoclinic. Microstructural analysis using TEM shows that the dominant slip systems of jadeite in one sample are (100)[001], (110)[001] and (1 1 0)1/2[110], while in another sample, no dislocations are observed. Abundant dislocations in quartz were accommodated by the dominant slip system (0001)[110], indicating basal glide and represents regional shearing during the exhumation process. This suggests that dislocation creep is the dominant fundamental deformation mechanism in jadeite under UHP conditions. The protoliths of jadeite-quartzite, metasedimentary rocks from the northern passive continental margin of the Yangtze craton, experienced the same deep subduction and were deformed under similar rheological conditions as other UHP eclogite, marble and paragneiss. Experimental UHP deformation of quartzo-feldspathic gneiss with a chemical composition similar to the bulk continental crust has shown that the formation of a jadeite,stishovite rock is associated with a density increase of the host rock similar to the eclogite conversion from basaltic protoliths. The resulting rock can be denser than the surrounding mantle pyrolite up to depths of 660 km (24 GPa). Thus, processes of deep continental subduction may be better-understood through understanding the rheology and mechanical behaviour of jadeite. Jadeite-quartzites such as those from the Shuanghe may be exhumed remnants of deeply-subducted slabs of continental crust, other parts of which subducted past the ,depth of no return', and remain in the deep mantle. [source] Remodeling of extracellular matrix at ovulation of the bovine ovarian follicleMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 10 2006H.F. Irving-Rodgers Abstract Using immunohistochemistry and RNA analyses we examined the fate of components of a newly identified matrix that develops between granulosa cells (focimatrix, abbreviated from focal intraepithelial matrix) and of the follicular basal lamina in ovulating bovine ovarian follicles. Pre- and postovulatory follicles were generated by treatment with estradiol (Day 1), progesterone (Days 1,10), and prostaglandin analogue (Day 9) with either no further treatment (Group 1, n,=,6) and or with 25 mg porcine LH (Day 11, Group 2, n,=,8 or Day 10, Group 3, n,=,8) and ovariectomy on Day 12 (12,14 hr post LH in Group 2, 38,40.5 hr in Group 3). In the time frame examined no loss of follicular basal lamina laminin chains ,2 and ,1 or nidogen 1 was observed. In the follicular basal lamina collagen type IV ,1 and perlecan were present prior to ovulation; after ovulation collagen type IV ,1 was discontinuously distributed and perlecan was absent. Versican in the theca interna adjacent to the follicular basal lamina in preovulatory follicles was not observed post ovulation, however, the granulosa cells then showed strong cytoplasmic staining for versican. Expression of versican isoforms V0, V1, and V3 was detected at all stages. Focimatrix was observed in preovulatory follicles. It contained collagen type IV ,1, laminins ,2 and ,1, nidogen 1 and perlecan and underwent changes in composition similar to that of the follicular basal lamina. In conclusion focimatrix and the follicular basal lamina are degraded at ovulation. Individual components are lost at different times. Mol. Reprod. Dev. © 2006 Wiley-Liss, Inc. [source] Short-Term Response of Land Birds to Ponderosa Pine RestorationRESTORATION ECOLOGY, Issue 4 2007William L. Gaines Abstract We monitored the short-term (>3 years) response of land birds to forest restoration treatments in Ponderosa pine forests located on the east slope of the North Cascade Range. Restoration treatments were designed to create stand structure and composition similar to pre-settlement forests, which were influenced by a frequent fire regime. Overall, avian community composition was changed as a result of the treatments. Cassin's Finch, Chipping Sparrow, and Yellow-rumped Warbler were found at higher densities in treated stands, whereas Mountain Chickadee, Western Tanager, and Red-breasted Nuthatch had higher densities in untreated stands. White-headed Woodpecker and Western Bluebird were only detected in the treated stands. Brown-headed Cowbird showed no response to treatments. We detected changes in the density of four of five foraging guilds in response to restoration treatments. Tree seedeaters, low understory and ground insectivores, and aerial insectivores all increased in density in treated stands. Overall, bark insectivores showed no density response to treatments. Tree foliage insectivore density was lower in treated than in untreated stands. Overall avian density, density of neotropical migrants, and density of some focal species were higher in treated stands. Monitoring should be continued to understand the longer-term (5,10 year) responses of land birds and to guide future forest restoration efforts. [source] TEOS,colloidal silica,PDMS-OH hybrid formulation used for stone consolidationAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2010Carmen Salazar-Hernández Abstract The consolidation of materials concept, which consists of introducing a chemical substance (consolidant) into degraded stone, has been applied to architectural conservation. Silicon compounds such as tetraethoxysilane (TEOS) are frequently used as a base for commercial consolidant formulations due to their ability to form a siloxane polymer such as SiO2. However, the silica xerogels deposited into the stone show poor performance and the gels obtained are non-porous and tend to crack during the drying stage. In order to avoid the fractures and to improve gel properties, we propose the synthesis of a hybrid consolidant based on TEOS and fillers such as colloidal silica (200 nm in diameter) and hydroxy-terminated polydimethylsiloxane (PDMS-OH). Both additives enhance gel properties such as porosity and elasticity, leading to the formation of non-fractured and permeable gels. Characterization of the hybrid xerogel was carried out by nitrogen adsorption and 29Si MAS-NMR. The properties of the hybrid xerogels were compared with those prepared from a formulation based on TEOS (T-ME) with a composition similar to a commercial product. In order to evaluate the effectiveness of the hybrid consolidant, it was applied to tuff-stone of historical monuments in the city of Guanajuato, Mexico. The tuff-stone was also treated with the formulation T-ME. Both treatments were studied by determining the percentage of consolidant deposited, evaluating changes in porosity and hardness of the treated stone. The applicability of the hybrid consolidant for the decayed tuff-stone is under study. Copyright © 2010 John Wiley & Sons, Ltd. [source] SAND FOR ROMAN GLASS PRODUCTION: AN EXPERIMENTAL AND PHILOLOGICAL STUDY ON SOURCE OF SUPPLY*ARCHAEOMETRY, Issue 3 2006A. SILVESTRI This paper reports the results of an experimental study performed on Campanian littoral sand, together with a careful philological analysis of Pliny's text concerning the production of glass using the above sand in order to verify its suitability. Accurate chemical and mineralogical characterization of sand samples and experimental glasses was carried out, proving the unsuitability of sand for glass production in its original state. Taking into account both the results of the philological analysis of Pliny's text and the mineralogical assemblage of the sand, a new hypothesis regarding Roman glass-making technology is proposed and tested here. The technology implies the production of ,quartz-enriched' sand by means of selective grindings according to the different degrees of hardness and cleavage of the mineralogical phases. Melting experiments, carried out on treated sand and in the temperature range compatible with Roman technology, yielded a glass with composition similar to those of typical Roman glasses. Therefore, new perspectives on the sources of supply of raw materials, hitherto debated, are opened up. [source] Mycenaean pottery from the Argolid and Achaia,a mineralogical approach where chemistry leaves unanswered questionsARCHAEOMETRY, Issue 2 2002A. Hein The chemical classification of Mycenaean pottery from the Northern Peloponnese by neutron activation analysis (NAA) resulted in two groups with very similar chemical compositions assigned to production centres in the Argolid and in Achaia, respectively. The statistical separation of these two groups on the basis only of their chemical composition was difficult, and not clear-cut for all of the examined samples. A complementary mineralogical examination by X-ray diffraction (XRD) of some selected samples indicated differences in the mineralogical composition, which confirmed the determined chemical differences. Furthermore, a clay sample was examined, which showed a composition similar to that of the pottery. [source] Invasion of a karst aquifer by hydrothermal fluids: evidence from stable isotopic compositions of cave mineralizationGEOFLUIDS (ELECTRONIC), Issue 2 2001S. H. Bottrell Abstract Mineral deposits in the Cupp-Coutunn/Promeszutochnaya cave system (Turkmenia, central Asia) record a phase of hydrothermal activity within a pre-existing karstic groundwater conduit system. Hydrothermal fluids entered the caves through fault zones and deposited sulphate, sulphide and carbonate minerals under phreatic conditions. Locally, intense alteration of limestone wall rocks also occurred at this stage. Elsewhere in the region, similar faults contain economic quantities of galena and elemental sulphur mineralization. Comparisons between the Pb and S isotope compositions of minerals found in cave and ore deposits confirm the link between economic mineralization and hydrothermal activity at Cupp-Coutunn. The predominance of sulphate mineralization in Cupp-Coutunn implies that the fluids were more oxidized in the higher permeability zone associated with the karst aquifer. A slight increase in the ,34S of sulphate minerals and a corresponding ,34S decrease in sulphides suggest that partial isotopic equilibration occurred during oxidation. Carbonate minerals indicate that the hydrothermal fluid was enriched in 18O (,18OSMOW , + 10,) relative to meteoric groundwater and seawater. Estimated values for ,13CDIC (,13CPDB , , 13,) are consistent with compositions expected for dissolved inorganic carbon (DIC) derived from the products of thermal decomposition of organic matter and dissolution of marine carbonate. Values derived for ,13CDIC and ,18Owater indicate that the hydrothermal fluid was of basinal brine origin, generated by extensive water,rock interaction. Following the hydrothermal phase, speleothemic minerals were precipitated under vadose conditions. Speleothemic sulphates show a bimodal sulphur isotope distribution. One group has compositions similar to the hydrothermal sulphates, whilst the second group is characterized by higher ,34S values. This latter group may either record the effects of microbial sulphate reduction, or reflect the introduction of sulphate-rich groundwater generated by the dissolution of overlying evaporites. Oxygen isotope compositions show that calcite speleothems were precipitated from nonthermal groundwater of meteoric origin. Carbonate speleothems are relatively enriched in 13C compared to most cave deposits, but can be explained by normal speleothem-forming processes under thin, arid-zone soils dominated by C4 vegetation. However, the presence of sulphate speleothems, with isotopic compositions indicative of the oxidation of hydrothermal sulphide, implies that CO2 derived by reaction of limestone with sulphuric acid (,condensation corrosion') contributed to the formation of 13C-enriched speleothem deposits. [source] Relics of the Mozambique Ocean in the central East African Orogen: evidence from the Vohibory Block of southern MadagascarJOURNAL OF METAMORPHIC GEOLOGY, Issue 1 2008N. JÖNS Abstract The Vohibory Block of south-western Madagascar is part of the East African Orogen, the formation of which is related to the assembly of the Gondwana supercontinent. It is dominated by metabasic rocks, which have chemical compositions similar to those of recent basalts from a mid-ocean ridge, back-arc setting and island-arc setting. The age of formation of protolith basalts has been dated at 850,700 Ma by U,Pb SHRIMP analysis of magmatic cores in zircon, pointing to an origin related to the Neoproterozoic Mozambique Ocean. The metabasic rocks are interpreted as representing components of an island arc with an associated back-arc basin. In the early stage of the Pan-African orogeny, these rocks experienced high-pressure amphibolite to granulite facies metamorphism (9,12 kbar, 750,880 °C), dated at 612 ± 5 Ma from metamorphic rims in zircon. The metamorphism was most likely related to accretion of the arc terrane to the margin of the Azania microcontinent (Proto-Madagascar) and closure of the back-arc basin. The main metamorphism is significantly older than high-temperature metamorphism in other tectonic units of southern Madagascar, indicating a distinct tectono-metamorphic history. [source] Geology and geochemistry of shallow drill cores from the Bosumtwi impact structure, GhanaMETEORITICS & PLANETARY SCIENCE, Issue 8 2003Daniel Boamah The interior of the structure is largely filled by the 8 km diameter Lake Bosumtwi, and the crater rim and region in the environs of the crater is covered by tropical rainforest, making geological studies rather difficult and restricted to road cuts and streams. In early 1999, we undertook a shallow drilling program to the north of the crater rim to determine the extent of the ejecta blanket around the crater and to obtain subsurface core samples for mineralogical, petrological, and geochemical studies of ejecta of the Bosumtwi impact structure. A variety of impactite lithologies are present, consisting of impact glassrich suevite and several types of breccia: lithic breccia of single rock type, often grading into unbrecciated rock, with the rocks being shattered more or less in situ without much relative displacement (autochthonous?), and lithic polymict breccia that apparently do not contain any glassy material (allochtonous?). The suevite cores show that melt inclusions are present throughout the whole length of the cores in the form of vesicular glasses with no significant change of abundance with depth. Twenty samples from the 7 drill cores and 4 samples from recent road cuts in the structure were studied for their geochemical characteristics to accumulate a database for impact lithologies and their erosion products present at the Bosumtwi crater. Major and trace element analyses yielded compositions similar to those of the target rocks in the area (graywacke-phyllite, shale, and granite). Graywacke-phyllite and granite dikes seem to be important contributors to the compositions of the suevite and the road cut samples (fragmentary matrix), with a minor contribution of Pepiakese granite. The results also provide information about the thickness of the fallout suevite in the northern part of the Bosumtwi structure, which was determined to be ,15 m and to occupy an area of ,1.5 km2. Present suevite distribution is likely to be caused by differential erosion and does not reflect the initial areal extent of the continuous Bosumtwi ejecta deposits. Our studies allow a comparison with the extent of the suevite at the Ries, another well-preserved impact structure. [source] Vesta, Vestoids, and the howardite, eucrite, diogenite group: Relationships and the origin of spectral differencesMETEORITICS & PLANETARY SCIENCE, Issue 6 2001T. H. Burbine All of the measured small asteroids (except for 2579 Spartacus) have reflectance spectra consistent with surface compositions similar to eucrites and howardites and consistent with all being derived from Vesta. None of the observed asteroids have spectra similar to diogenites. We find no spectral distinction between the 15 objects tabulated as members of the Vesta dynamical family and 6 of the 7 sampled "non-family" members that reside just outside the semi-major axis (a), eccentricity (e), and inclination (i) region of the family. The spectral consistency and close orbital (a-e-i) match of these "non-family" objects to Vesta and the Vesta family imply that the true bounds of the family extend beyond the subjective cut-off for membership. Asteroid 2579 Spartacus has a spectrum consistent with a mixture of eucritic material and olivine. Spartacus could contain olivine-rich material from Vesta's mantle or may be unrelated to Vesta altogether. Laboratory measurements of the spectra of eucrites show that samples having nearly identical compositions can display a wide range of spectral slopes. Finer particle sizes lead to an increase in the slope, which is usually referred to as reddening. This range of spectral variation for the best-known meteoritic analogs to the Vestoids, regardless of whether they are actually related to each other, suggests that the extremely red spectral slopes for some Vestoids can be explained by very fine-grained eucritic material on their surfaces. [source] | ||||||||||||||||