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1.
Sci Adv ; 8(50): eade2067, 2022 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-36525483

RESUMO

The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: 16O-rich (associated with refractory inclusions) and 16O-poor (associated with chondrules). Both the 16O-rich and 16O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outward. The abundance ratios of the 16O-rich to 16O-poor minerals in Ryugu and CI chondrites are higher than in other carbonaceous chondrite groups but are similar to that of comet 81P/Wild2, suggesting that Ryugu and CI chondrites accreted in the outer Solar System closer to the accretion region of comets.

2.
Sci Adv ; 8(46): eadd8141, 2022 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-36264823

RESUMO

Little is known about the origin of the spectral diversity of asteroids and what it says about conditions in the protoplanetary disk. Here, we show that samples returned from Cb-type asteroid Ryugu have Fe isotopic anomalies indistinguishable from Ivuna-type (CI) chondrites, which are distinct from all other carbonaceous chondrites. Iron isotopes, therefore, demonstrate that Ryugu and CI chondrites formed in a reservoir that was different from the source regions of other carbonaceous asteroids. Growth and migration of the giant planets destabilized nearby planetesimals and ejected some inward to be implanted into the Main Belt. In this framework, most carbonaceous chondrites may have originated from regions around the birthplaces of Jupiter and Saturn, while the distinct isotopic composition of CI chondrites and Ryugu may reflect their formation further away in the disk, owing their presence in the inner Solar System to excitation by Uranus and Neptune.

3.
Science ; : eabn7850, 2022 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-35679354

RESUMO

Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measure the mineralogy, bulk chemical and isotopic compositions of Ryugu samples. They are mainly composed of materials similar to carbonaceous chondrite meteorites, particularly the CI (Ivuna-type) group. The samples consist predominantly of minerals formed in aqueous fluid on a parent planetesimal. The primary minerals were altered by fluids at a temperature of 37 ± 10°C, [Formula: see text] (Stat.) [Formula: see text] (Syst.) million years after formation of the first solids in the Solar System. After aqueous alteration, the Ryugu samples were likely never heated above ~100°C. The samples have a chemical composition that more closely resembles the Sun's photosphere than other natural samples do.

4.
Sci Adv ; 7(40): eabg8329, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34586847

RESUMO

Calcium-aluminum­rich inclusions (CAIs) in meteorites carry crucial information about the environmental conditions of the nascent Solar System prior to planet formation. Based on models of 50V­10Be co-production by in-situ irradiation, CAIs are considered to have formed within ~0.1 AU from the proto-Sun. Here, we present vanadium (V) and strontium (Sr) isotopic co-variations in fine- and coarse-grained CAIs and demonstrate that kinetic isotope effects during partial condensation and evaporation best explain V isotope anomalies previously attributed to solar particle irradiation. We also report initial excesses of 10Be and argue that CV CAIs possess essentially a homogeneous level of 10Be, inherited during their formation. Based on numerical modeling of 50V­10Be co-production by irradiation, we show that CAI formation during protoplanetary disk build-up likely occurred at greater heliocentric distances than previously considered, up to planet-forming regions (~1AU), where solar particle fluxes were sufficiently low to avoid substantial in-situ irradiation of CAIs.

5.
Geochim Cosmochim Acta ; 269: 639-660, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-32020947

RESUMO

We carried out a coordinated mineralogical and isotopic study of a Wark-Lovering (WL) rim on a Ca,Al-rich inclusion (CAI) from the reduced CV3 chondrite Vigarano. The outermost edge of the CAI mantle is mineralogically and texturally distinct compared to the underlying mantle that is composed of coarse, zoned melilite (Åk~10-60) grains. The mantle edge contains fine-grained gehlenite with hibonite and rare grossite that likely formed by rapid crystallization from a melt enriched in Ca and Al. These gehlenite and hibonite layers are surrounded by successive layers of spinel, zoned melilite (Åk~0-10), zoned diopside that grades outwards from Al,Ti-rich to Al,Ti-poor, and forsteritic olivine intergrown with diopside. These layered textures are indicative of sequential condensation of spinel, melilite, diopside, and forsterite onto hibonite. Anorthite occurs as a discontinuous layer that corrodes adjacent melilite and Al-diopside, and appears to have replaced them, probably even later than the forsterite layer formation. Based on these observations, we conclude that the WL rim formation was initiated by flash melting and extensive evaporation of the original inclusion edge, followed by subsequent gas-solid reactions under highly dynamic conditions. All the WL rim minerals are 16O-rich (Δ17O = ~-23‰), indicating their formation in an 16O-rich nebular reservoir. Our Al-Mg measurements of hibonite, spinel, and diopside from the WL rim, as well as spinel and Al,Ti-diopside in the core, define a single, well-correlated isochron with an inferred initial 26Al/27Al ratio of (4.94 ± 0.12) × 10-5. This indicates that the WL rim formed shortly after the host CAI. In contrast, the lack of 26Mg excesses in the WL rim anorthite suggest its later formation or later isotopic disturbance in the solar nebula, after 26Al had decayed.

6.
ACR Open Rheumatol ; 1(1): 26-36, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31777777

RESUMO

OBJECTIVE: We sought to determine if any histopathologic component of the pulmonary microcirculation can distinguish systemic sclerosis (SSc)-related pulmonary fibrosis (PF) with and without pulmonary hypertension (PH). METHODS: Two pulmonary pathologists blindly evaluated 360 histologic slides from lungs of 31 SSc-PF explants or autopsies with (n = 22) and without (n = 9) PH. The presence of abnormal small arteries, veins, and capillaries (pulmonary microcirculation) was semiquantitatively assessed in areas of preserved lung architecture. Capillary proliferation (CP) within the alveolar walls was measured by its distribution, extent (CP % involvement), and maximum number of layers (maximum CP). These measures were then evaluated to determine the strength of their association with right heart catheterization-proven PH. RESULTS: Using consensus measures, all measures of CP were significantly associated with PH. Maximum CP had the strongest association with PH (P = 0.013; C statistic 0.869). Maximum CP 2 or more layers and CP % involvement 10% or greater were the optimal thresholds that predicted PH, both with a sensitivity of 56% and specificity of 91%. The CP was typically multifocal rather than focal or diffuse and was associated with a background pattern of usual interstitial pneumonia. There was a significant but weaker relationship between the presence of abnormal small arteries and veins and PH. CONCLUSION: In the setting of advanced SSc-PF, the histopathologic feature of the pulmonary microcirculation best associated with PH was capillary proliferation in architecturally preserved lung areas.

7.
Chem Erde ; 79(4)2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32020946

RESUMO

A coordinated mineralogical and oxygen isotopic study of four fine-grained calcium-, aluminum-rich inclusions (CAIs) from the ALHA77307 CO3.0 carbonaceous chondrite was conducted. Three of the inclusions studied, 05, 1-65, and 2-119, all have nodular structures that represent three major groups, melilite-rich, spinel-rich, and hibonite-rich, based on their primary core mineral assemblages. A condensation origin was inferred for these CAIs. However, the difference in their primary core mineralogy reflects unique nebular environments in which multiple gas-solid reactions occurred under disequilibrium conditions to form hibonite, spinel, and melilite with minor perovskite and Al,Ti-rich diopside. A common occurrence of a diopside rim on the CAIs records a widespread event that marks the end of their condensation as a result of isolation from a nebular gas. An exception is a rare inclusion 2-112 that contains euhedral spinel crystals embedded in melilite, suggesting this CAI had been re-melted. All of the fine-grained CAIs analyzed in ALHA77307 are uniformly 16O-rich with an average Δ17O value of ~-22 ± 5‰ (2σ), indicating no apparent correlation between their textures and oxygen isotopic compositions. We therefore conclude that a prevalent 16O-rich gas reservoir existed in a region of the solar nebula where CO3 fine-grained CAIs formed, initially by condensation and then later, some of them were reprocessed by melting event(s).

8.
Proc Natl Acad Sci U S A ; 115(41): 10287-10292, 2018 10 09.
Artigo em Inglês | MEDLINE | ID: mdl-30249648

RESUMO

Hydrosphere interactions and alteration of the terrestrial crust likely played a critical role in shaping Earth's surface, and in promoting prebiotic reactions leading to life, before 4.03 Ga (the Hadean Eon). The identity of aqueously altered material strongly depends on lithospheric cycling of abundant and water-soluble elements such as Si and O. However, direct constraints that define the character of Hadean sedimentary material are absent because samples from this earliest eon are limited to detrital zircons (ZrSiO4). Here we show that concurrent measurements of Si and O isotope ratios in Phanerozoic and detrital pre-3.0 Ga zircon constrain the composition of aqueously altered precursors incorporated into their source melts. Phanerozoic zircon from (S)edimentary-type rocks contain heterogeneous δ18O and δ30Si values consistent with assimilation of metapelitic material, distinct from the isotopic character of zircon from (I)gneous- and (A)norogenic-type rocks. The δ18O values of detrital Archean zircons are heterogeneous, although yield Si isotope compositions like mantle-derived zircon. Hadean crystals yield elevated δ18O values (vs. mantle zircon) and δ30Si values span almost the entire range observed for Phanerozoic samples. Coupled Si and O isotope data represent a constraint on Hadean weathering and sedimentary input into felsic melts including remelting of amphibolites possibly of basaltic origin, and fractional addition of chemical sediments, such as cherts and/or banded iron formations (BIFs) into source melts. That such sedimentary deposits were extensive enough to change the chemical signature of intracrustal melts suggests they may have been a suitable niche for (pre)biotic chemistry as early as 4.1 Ga.


Assuntos
Isótopos/análise , Espectrometria de Massas/métodos , Isótopos de Oxigênio/análise , Silicatos/análise , Silicatos/química , Silício/análise , Zircônio/análise , Zircônio/química , Austrália , Sedimentos Geológicos/química , África do Sul
9.
J Am Chem Soc ; 131(11): 3998-4005, 2009 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-19243183

RESUMO

Mesostructured silica synthesized using cetyltriethylammonium (CTEA) ion as the pore-directing agent in acidic environments was ready to have interfacial anions exchanged at ambient temperature. In situ techniques including small-angle X-ray scattering (SAXS) and optical microscopy were used to examine the structural and morphological changes of the as-made mesostructured materials, and pyrene fluorescence quenching experiment was used to probe the variation in interfacial environment during the anion-exchange processes. About one-half of the interfacial anions between the silica framework and micelle were exchanged based on the fluorescence quenching experiments of pyrene, which was dissolved in the hydrophobic core of the micelle. Altering in the pore structure and the architecture of the silica framework was observed when the interfacial anions were exchanged by anions of higher salting-in power. The resultant phase transformation and morphological change were always toward pore structures of lower curvature. The influence of anion follows the Hofmeister series commonly encountered in macromolecular and biological systems. The mesophase transformation induced by the interfacial anion exchange provides a unique technique to study anions which are not yet included in the Hofmeister series.


Assuntos
Transição de Fase , Dióxido de Silício/química , Micelas , Porosidade
10.
Science ; 314(5806): 1724-8, 2006 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-17170292

RESUMO

Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild 2 particle fragments; however, extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single (17)O-enriched circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is (16)O-enriched, like refractory inclusions in meteorites, suggesting that Wild 2 contains material formed at high temperature in the inner solar system and transported to the Kuiper belt before comet accretion.


Assuntos
Isótopos de Carbono/análise , Deutério/análise , Isótopos/análise , Meteoroides , Isótopos de Nitrogênio/análise , Isótopos de Oxigênio/análise , Hidrogênio/análise , Neônio/análise , Gases Nobres/análise , Astronave
11.
Pharmacology ; 75(2): 98-110, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16103741

RESUMO

The effects of 7-bromo-1,4-dihydro-2-phenyl-4,4-bis(4-pyridinylmethyl)2H-isoquinolin-3-one dihydrochloride (BDPBI) on induction of action potential bursts were studied pharmacologically on the RP4 central neuron of the giant African snail (Achatina fulica Ferussac). The effects of m-3M3FBS, a phospholipase activator and HTMT, a histamine (H1) receptor agonist, on the neuron were also tested. The RP4 neuron showed spontaneous firing of action potential. Extracellular application of BDPBI (150 micromol/l) reversibly elicited bursts of potential (BoP) on the neuron. m-3M3FBS and HTMT also elicited BoP on the RP4 neuron. The BoP elicited by BDPBI were blocked by U73122 (6 micromol/l), a compound commonly used as a phospholipase C (PLC) inhibitor. Neomycin (3.5 mmol/l), a high-magnesium solution (30 mmol/l), replacing the physiological sodium ion with lithium ion or adding diphenhydramine, chloropheniramine decreased the BoP elicited by BDPBI. The BoP elicited by BDPBI were not inhibited after administration with (1) prazosin, propranolol, atropine, d-tubocurarine, hexamethonium, haloperidol, cimetidine, (2) calcium-free solution, (3) high-potassium (12 mmol/l) solution, and (4) pretreatment with KT-5720. The BoP elicited by HTMT was not inhibited after administration of diphenhydramine or chloropheniramine. Voltage-clamped studies revealed that BDPBI decreased the amplitudes of calcium and steady-state outward currents while it did not alter the amplitude of the fast inward current. No negative slope relationship of the steady-state current voltage relationship was found in BDPBI-treated neurons. It is concluded that BDPBI reversibly elicited BoP in the central snail neuron. The effect was not due to (1) the extracellular calcium ion fluxes, or (2) the activation of cholinergic, adrenergic or histamine receptors. The BDPBI-elicited BoP were dependent on the phospholipase activity in the neuron.


Assuntos
Isoquinolinas/farmacologia , Neurônios/efeitos dos fármacos , Piridinas/farmacologia , Potenciais de Ação/efeitos dos fármacos , Animais , Cálcio/farmacologia , Carbazóis/farmacologia , Clorfeniramina/farmacologia , Cimetidina/farmacologia , Estrenos/farmacologia , Indóis/farmacologia , Lítio/farmacologia , Magnésio/farmacologia , Neomicina/farmacologia , Neurônios/fisiologia , Fosfolipases/fisiologia , Potássio/farmacologia , Pirróis/farmacologia , Pirrolidinonas/farmacologia , Caramujos , Sulfonamidas/farmacologia
12.
Pharmacology ; 73(2): 57-69, 2005 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-15452414

RESUMO

The effects of 2,3-butanedione monoxime (BDM) on induction of action potential bursts were studied pharmacologically on the RP4 central neuron of giant African snail (Achatina fulica Ferussac). The effect of okadaic acid on the neuron was also tested. The RP4 neuron showed a spontaneous firing of action potential. Okadaic acid (1 micromol/l) did not alter the frequency of spontaneous action potential while BDM (3 mmol/l) reversibly elicited bursts of potential (BoP) of the RP4 neuron. The BoP elicited by BDM (3 mmol/l) were reversed 20 min after incubation with diazoxide (500 micromol/l) while the BoP were not altered in preparations treated with okadaic acid and BDM. The BDM-elicited BoP were not inhibited after administration with (a) hexamethonium (100 micromol/l), (b) atropine (1 mmol/l), (c) d-tubocurarine (100 micromol/l), (d) prazosin (100 micromol/l), (e) propranolol (100 micromol/l), (f) calcium-free solution, (g) high K(+) (12 mmol/l) or (h) with high Mg(2+) (30 mmol/l) solutions. The BDM-elicited BoP were inhibited by pretreatment with KT-5720 (10 micromol/l) or H89 (10 micromol/l), the protein kinase A inhibitors. However, the BoP were not affected after application of chelerythrine (10 micromol/l) or Ro 31-8220 (10 micromol/l), the protein kinase C inhibitors. Voltage-clamped studies revealed that BDM elicited a negative slope resistance (NSR) at membrane potentials between -50 and -10 mV. The NSR was not detectable at the same membrane potential in control RP4 neuron. It is suggested that the BoP elicited by BDM were not due to (1) the synaptic effects of neurotransmitters; (2) the activation of cholinergic, adrenergic receptors, or (3) phosphatase activity of the neuron. The BDM-elicited BoP were dependent on the protein kinase A related cAMP in the neuron and the delayed outward K(+) current may contribute to the BDM-elicited BoP.


Assuntos
Potenciais de Ação/efeitos dos fármacos , Diacetil/análogos & derivados , Diacetil/farmacologia , Neurônios/fisiologia , Animais , Proteínas Quinases Dependentes de AMP Cíclico/antagonistas & inibidores , Proteínas Quinases Dependentes de AMP Cíclico/fisiologia , Gânglios dos Invertebrados/citologia , Gânglios dos Invertebrados/efeitos dos fármacos , Gânglios dos Invertebrados/fisiologia , Técnicas In Vitro , Neurônios/efeitos dos fármacos , Ácido Okadáico/farmacologia , Técnicas de Patch-Clamp , Monoéster Fosfórico Hidrolases/fisiologia , Proteína Quinase C/antagonistas & inibidores , Proteína Quinase C/fisiologia , Receptores Adrenérgicos/fisiologia , Receptores Colinérgicos/fisiologia , Caramujos
13.
Chem Commun (Camb) ; (23): 2854-5, 2002 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-12478780

RESUMO

Solvent evaporation upon drying the precipitate was found to be the key factor for the phase transformation of cubic mesoporous silica SBA-1 to hexagonal SBA-3 studied by in-situ X-ray diffraction and 29Si solid state NMR on the precipitates formed various crystallisation conditions.

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