Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 98
Filtrar
Mais filtros

Bases de dados
Tipo de documento
Intervalo de ano de publicação
1.
Anal Chem ; 96(1): 170-178, 2024 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-38155534

RESUMO

Characterization of the elemental distribution of samples with rough surfaces has been strongly desired for the analysis of various natural and artificial materials. Particularly for pristine and rare analytes with micrometer sizes embedded on specimen surfaces, non-invasive and matrix effect-free analysis is required without surface polishing treatment. To satisfy these requirements, we proposed a new method employing the sequential combination of two imaging modalities, i.e., microenergy-dispersive X-ray fluorescence (micro-XRF) and Raman micro-spectroscopy. The applicability of the developed method is tested by the quantitative analysis of cation composition in micrometer-sized carbonate grains on the surfaces of intact particles sampled directly from the asteroid Ryugu. The first step of micro-XRF imaging enabled a quick search for the sparsely scattered and micrometer-sized carbonates by the codistributions of Ca2+ and Mn2+ on the Mg2+- and Fe2+-rich phyllosilicate matrix. The following step of Raman micro-spectroscopy probed the carbonate grains and analyzed their cation composition (Ca2+, Mg2+, and Fe2+ + Mn2+) in a matrix effect-free manner via the systematic Raman shifts of the lattice modes. The carbonates were basically assigned to ferroan dolomite bearing a considerable amount of Fe2+ + Mn2+ at around 10 atom %. These results are in good accordance with the assignments reported by scanning electron microscopy-energy-dispersive X-ray spectroscopy, where the thin-sectioned and surface-polished Ryugu particles were applicable. The proposed method requires neither sectioning nor surface polishing; hence, it can be applied to the remote sensing apparatus on spacecrafts and planetary rovers. Furthermore, the non-invasive and matrix effect-free characterization will provide a reliable analytical tool for quantitative analysis of the elemental distribution on the samples with surface roughness and chemical heterogeneity at a micrometer scale, such as art paintings, traditional crafts with decorated shapes, as well as sands and rocks with complex morphologies in nature.

2.
Nature ; 555(7694): 89-93, 2018 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-29493592

RESUMO

Active volcanic hotspots can tap into domains in Earth's deep interior that were formed more than two billion years ago. High-precision data on variability in tungsten isotopes have shown that some of these domains resulted from differentiation events that occurred within the first fifty million years of Earth history. However, it has not proved easy to resolve analogous variability in neodymium isotope compositions that would track regions of Earth's interior whose composition was established by events occurring within roughly the first five hundred million years of Earth history. Here we report 142Nd/144Nd ratios for Réunion Island igneous rocks, some of which are resolvably either higher or lower than the ratios in modern upper-mantle domains. We also find that Réunion 142Nd/144Nd ratios correlate with helium-isotope ratios (3He/4He), suggesting parallel behaviour of these isotopic systems during very early silicate differentiation, perhaps as early as 4.39 billion years ago. The range of 142Nd/144Nd ratios in Réunion basalts is inconsistent with a single-stage differentiation process, and instead requires mixing of a conjugate melt and residue formed in at least one melting event during the Hadean eon, 4.56 billion to 4 billion years ago. Efficient post-Hadean mixing nearly erased the ancient, anomalous 142Nd/144Nd signatures, and produced the relatively homogeneous 143Nd/144Nd composition that is characteristic of Réunion basalts. Our results show that Réunion magmas tap into a particularly ancient, primitive source compared with other volcanic hotspots, offering insight into the formation and preservation of ancient heterogeneities in Earth's interior.

3.
Proc Natl Acad Sci U S A ; 118(23)2021 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-34074760

RESUMO

Globally distributed kimberlites with broadly chondritic initial 143Nd-176Hf isotopic systematics may be derived from a chemically homogenous, relatively primitive mantle source that remained isolated from the convecting mantle for much of the Earth's history. To assess whether this putative reservoir may have preserved remnants of an early Earth process, we report 182W/184W and 142Nd/144Nd data for "primitive" kimberlites from 10 localities worldwide, ranging in age from 1,153 to 89 Ma. Most are characterized by homogeneous µ182W and µ142Nd values averaging -5.9 ± 3.6 ppm (2SD, n = 13) and +2.7 ± 2.9 ppm (2SD, n = 6), respectively. The remarkably uniform yet modestly negative µ182W values, coupled with chondritic to slightly suprachondritic initial 143Nd/144Nd and 176Hf/177Hf ratios over a span of nearly 1,000 Mya, provides permissive evidence that these kimberlites were derived from one or more long-lived, early formed mantle reservoirs. Possible causes for negative µ182W values among these kimberlites include the transfer of W with low µ182W from the core to the mantle source reservoir(s), creation of the source reservoir(s) as a result of early silicate fractionation, or an overabundance of late-accreted materials in the source reservoir(s). By contrast, two younger kimberlites emplaced at 72 and 52 Ma and characterized by distinctly subchondritic initial 176Hf/177Hf and 143Nd/144Nd have µ182W values consistent with the modern upper mantle. These isotopic compositions may reflect contamination of the ancient kimberlite source by recycled crustal components with µ182W ≥ 0.

4.
Conscious Cogn ; 113: 103552, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-37453190

RESUMO

Our main goal in these experiments was to examine whether affective valence plays a role in judgments of control (JoC) in intentional action. To test this, we asked participants to completevariationsofasimple aiming task in which words appeared in place of clicked targets. The affective content of the words was manipulated during the experiments but was not contingent on participants' performance. Throughout the task, participants were periodically asked to judge their JoC.Thus, JoC judgments in this task included contributions of a well-established cue to judgments of control, task performance, and a source of affect that was not related to task performance. We found thatmetacognitions of controlvaried consistentlyacross levels of affect, with stronger judgments of being in control for conditions with positive outcome words (e.g., 'puppy') and the weaker judgments of being in control for conditions with negative outcome words (e.g.,'killer').These results suggestaffective outcomes can influence JoC, even though the outcomes are not related to performance.


Assuntos
Julgamento , Análise e Desempenho de Tarefas , Humanos
5.
Molecules ; 28(5)2023 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-36903495

RESUMO

Two species within the Lamiaceae (mint) family, Agastache urticifolia and Monardella odoratissima, are aromatic plants that are native to the Intermountain Region (USA). Essential oil produced through steam distillation was examined to establish the essential oil yield and both the achiral and chiral aromatic profiles of both plant species. The resulting essential oils were analyzed by GC/MS, GC/FID, and MRR (molecular rotational resonance). For A. urticifolia and M. odoratissima, achiral essential oil profiles were largely composed of limonene (71.0%, 27.7%), trans-ß-ocimene (3.6%, 6.9%), and pulegone (15.9%, 4.3%), respectively. Between the two species, eight chiral pairs were analyzed and, interestingly, the dominant enantiomer (calculated as ee%) of limonene and pulegone switched between the two species. Where enantiopure standards were not commercially available, MRR was used as a reliable analytical technique for chiral analysis. This study verifies the achiral profile for A. urticifolia and, for the first time to the authors' knowledge, establishes the achiral profile for M. odoratissima and chiral profile for both species. Additionally, this study confirms the utility and practicality of using MRR for determining chiral profiles in essential oils.


Assuntos
Agastache , Lamiaceae , Óleos Voláteis , Limoneno , Utah , Estereoisomerismo
6.
Psychol Res ; 86(2): 651-666, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33839940

RESUMO

Actions can be identified at a range of levels, from higher level, outcome-related descriptions to lower level, movement-related descriptions. But how do these levels of identification influence the experience of control (agency) over a task? We addressed the relation between the level of action identification and agency using a hierarchical task modeled from typing. Participants memorized letter sequences and reported them by moving a cursor to targets that contained letters. To manipulate lower level (aiming) difficulty, the targets were either large or small. To manipulate higher level (memory) difficulty, the letter sequences were either constant or random within a block. We found effects of higher and lower level difficulty on agency and action identification. Moreover, we found interactive effects of higher and lower level difficulty on performance. We discuss these findings in terms of contributions to the study of agency, and some differences from the results of previous studies of action identification.


Assuntos
Movimento , Desempenho Psicomotor , Humanos
7.
Molecules ; 27(9)2022 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-35566129

RESUMO

Ocimum campechianum Mill. (Peruvian basil) is an essential oil-bearing plant of the Lamiaceae family. Volatile oil produced through steam distillation of Peruvian basil was examined to establish the aromatic and stable isotope profiles of samples (n = 9) from three different cultivated plots in Peru. The resulting essential oils were analyzed by GC/FID, GC/MS, and GC/IRMS. In accordance with findings from other researchers, multiple chemotypes, defined by the most abundant aromatic compounds, exist within these populations. Overall, 55% of samples are the eugenol chemotype (values ranging 15.4-30.2%), 33% are the methyl eugenol chemotype (values ranging 68.1-68.7%), and a single sample is a mixture of both chemotypes, containing high levels of both eugenol (38.1%) and methyl eugenol (8.6%). Stable isotope ratios, δ2H and δ13C, performed on prominent compounds provide supporting data for distinguishing chemotypes. Complete aromatic profiles, stable isotope ratios, and essential oil yield are established for each sample. This study confirms the existence of multiple chemotypes and, for the first time, to the author's best knowledge, establishes stable isotope ratios for O. campechianum essential oil, which proves a useful tool in further investigating plant metabolism and determining essential oil authenticity.


Assuntos
Lamiaceae , Ocimum basilicum , Ocimum , Óleos Voláteis , Eugenol/análise , Isótopos , Peru , Óleos de Plantas/análise
8.
Molecules ; 26(8)2021 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-33920647

RESUMO

Lavandula angustifolia Mill. (lavender) is an essential-oil-bearing plant in the Lamiaceae family. Volatile oil produced through the steam distillation of lavender was examined to establish the essential oil yield and aromatic profile from each portion of the plant-namely, the corolla, calyx, leaf, and whole flowering top. The resulting essential oils were analyzed by GC-FID and GC-MS. The different plant parts generally shared similar compounds but in varying relative percentages. Aromatic profiles of the whole flowering top and calyx were similar, with prominent compounds being linalool acetate (34.3%, 32.0%), linalool (26.5%, 32.9%), lavandulyl acetate (5.6%, 4.9%), terpinen-4-ol (5.3%, 7.0%), and (Z)-ß-ocimene (4.5%, 5.4%), respectively. Aromatic profiles for the corolla and leaf were unique. Prominent aromatic compounds of the corolla included linalool acetate (18.4%), linalool (10.8%), epi-α-cadinol (10.0%), borneol (7.3%), and lavandulyl acetate (6.3%). Prominent aromatic compounds of the leaf included epi-α-cadinol (19.8%), γ-cadinene (11.0%), borneol (6.0%), caryophyllene oxide (4.9%), and bornyl acetate (4.8%). Complete profiles and essential oil yields of corolla, calyx, leaf, and whole flowering top were established. This study establishes the influence the corolla, calyx, and leaf exert on the aromatic profile of the whole flowering top and provides insight into authentication of lavender essential oil.


Assuntos
Flores/química , Lavandula/química , Óleos Voláteis/química , Folhas de Planta/química , Acetatos/química , Destilação , Monoterpenos/química , Óleos Voláteis/classificação , Óleos de Plantas/química , Terpenos/química
9.
Anesth Analg ; 131(5): 1566-1572, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-33079880

RESUMO

BACKGROUND: Endoscopic retrograde cholangiopancreatography (ERCP) patients typically receive either tubeless anesthesia or general endotracheal anesthesia (GETA). Patients receiving propofol-based total intravenous anesthesia (TIVA) are at higher risk of sedation-related adverse events (SRAEs) than patients receiving GETA, primarily due to the need for additional airway maneuvers. The increasing use of non-operating room (OR) anesthesia and the perception of a higher incidence of adverse outcomes in non-OR areas has led to the development of devices to improve safety while maintaining efficiency. The purpose of this study was to evaluate if the LMA Gastro™ could be used as a safe alternative to tubeless anesthesia for successfully completing ERCPs. METHODS: Eligible subjects were identified within the patient population at MD Anderson Cancer Center. Inclusion criteria consisted of adult patients (≥18 years old) scheduled for elective ERCP with TIVA. This was a prospective observational study in which the following data were collected: number of attempts and time to successful supraglottic airway (SGA) placement, vital signs, peripheral oxygen saturation (SpO2), median end-tidal CO2, practitioner satisfaction, and any complications. RESULTS: A total of 30 patients were included in this study. The overall rate of successful SGA placement within 3 attempts was 96.7% (95% confidence interval [CI], 82.8-99.9) or 29/30. The rate of successful ERCP with SGA placement within 3 attempts was 93.3% (95% CI, 77.9-99.2) or 28/30. Both the gastroenterologist and anesthesiologist reported satisfaction with the device in 90% of the cases (in 66.7% of the cases both anesthesiologist and gastroenterologist scored the device a 7/7 for satisfaction). Patients maintained an SpO2 of 95%-100% from induction to discharge, with the exception of 1 patient who had an SpO2 of 93%. The median end-tidal CO2 during the procedure for all patients was 35 mm Hg. Observed aspiration did not occur in any patient. Symptoms of hoarseness (13.3%), mouth soreness (6.7%), sore throat (6.6%), and minor bleeding/cuts/redness/change in taste to the tongue (3.3%) were determined through patient questioning before postanesthesia care unit (PACU) discharge. CONCLUSIONS: Our study suggests that the LMA Gastro might be a safe alternative for ERCP procedures. There was a high level of practitioner satisfaction. Only minor complications, such as hoarseness, mouth or throat soreness, or minor trauma to the tongue were experienced by patients. Similar incidences of complications may occur with GETA and tubeless anesthesia. The procedure was well tolerated by all patients; all patients maintained adequate oxygenation and required only minimal blood pressure support.


Assuntos
Colangiopancreatografia Retrógrada Endoscópica/efeitos adversos , Máscaras Laríngeas/efeitos adversos , Adulto , Idoso , Idoso de 80 Anos ou mais , Manuseio das Vias Aéreas , Anestesiologistas , Dióxido de Carbono/sangue , Colangiopancreatografia Retrógrada Endoscópica/métodos , Feminino , Gastroenterologistas , Rouquidão/epidemiologia , Rouquidão/etiologia , Humanos , Masculino , Pessoa de Meia-Idade , Oxigênio/sangue , Segurança do Paciente , Faringite/epidemiologia , Faringite/etiologia , Complicações Pós-Operatórias/epidemiologia , Estudos Prospectivos , Língua/lesões
10.
Psychol Res ; 84(1): 88-98, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29330595

RESUMO

We examined the hypothesis that skilled performance is monitored on the basis of fluency, where fluency is operationally defined as temporal regularity or rhythmicity rather than speed. Since error is often associated with variable timing, we tested the possibility that people use varied timing as a metacognitive cue. Using a sequential counting task, which may be representative of the broader class of skilled, multi-step tasks, we found that shifting between irregular and regular timing led to greater confidence ratings when the timing associated with the task was regular. We argue that regular, consistent timing, when compared directly to irregular timing, produced feelings of fluent task performance, leading to increased confidence. In the first experiment, we demonstrated that both accuracy and confidence were higher when participants completed a task presented with regular timing. In the second experiment, we found a dissociation between accuracy and confidence, strengthening the argument that individuals relied on monitoring of fluency to support their metacognitive judgments. In Study 3 and an assessment of naïve beliefs, we ruled out alternative explanations for these findings.


Assuntos
Conscientização/fisiologia , Sinais (Psicologia) , Julgamento/fisiologia , Metacognição/fisiologia , Desempenho Psicomotor/fisiologia , Adulto , Feminino , Humanos , Masculino , Estudantes , Universidades , Adulto Jovem
11.
Psychol Sci ; 29(4): 645-655, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29442592

RESUMO

We often remember information without its source (e.g., word or picture format). This phenomenon has been studied extensively in long-term memory but rarely in the context of short-term working memory (WM), which leaves open the question of whether source amnesia can result from a lack of memory encoding rather than forgetting. This study provided a series of striking and novel demonstrations showing participants' inability to report the source of a color representation immediately after that color was used in a task and stored in memory. These counterintuitive findings occurred when participants repeatedly judged the congruency between two color representations from one single object (i.e., color and identity of a color word) or two distinct objects (i.e., color of a square and identity of a color word) and then were unexpectedly asked to report the source of one color representation. These discoveries suggest that source information is often not stored in WM.


Assuntos
Percepção de Cores , Memória de Curto Prazo , Estimulação Luminosa , Percepção Visual , Amnésia/fisiopatologia , Atenção , Humanos , Tempo de Reação
12.
Nature ; 541(7638): 468-470, 2017 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-28128233
13.
Public Health Nurs ; 35(5): 369-378, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29770502

RESUMO

OBJECTIVE: To examine the occurrence of psychosocial risk factors among expectant fathers whose female partners were enrolled in prenatal home visiting services. DESIGN: Cross-sectional, exploratory, quantitative design. SAMPLE: Expectant father-mother pairs were recruited from two urban home visiting programs to participate in a randomized controlled trial of a father advocate intervention. The study sample consisted of 66 father-mother pairs who completed structured interviews at baseline, before randomization. MEASUREMENTS: Participants were interviewed using a structured questionnaire. This study focused on their responses related to 11 psychosocial risk factors, as measured by the Brief Risk Overview (BRO) for men and the Prenatal Risk Overview (PRO) for pregnant women. RESULTS: Moderate- or high-risk classification of psychosocial risk factors was prevalent among expectant fathers. The risk factors that fathers reported were diverse, related to their basic needs, social support, mental health, and substance use; risk factors frequently co-occurred. Fathers' and mothers' total risk scores, calculated as a composite of all 11 risk factors, were significantly correlated. CONCLUSIONS: Expectant fathers who have a partner enrolled in home visiting would benefit from psychosocial risk screening. Addressing fathers' risk factors may improve paternal health, their involvement in parenting, and the well-being of their partners and children.


Assuntos
Pai/psicologia , Visita Domiciliar/estatística & dados numéricos , Saúde Mental , Mães/psicologia , Poder Familiar/psicologia , Transtornos Relacionados ao Uso de Substâncias/diagnóstico , Adulto , Estudos Transversais , Feminino , Humanos , Masculino , Gravidez , Fatores de Risco , Parceiros Sexuais/psicologia , Inquéritos e Questionários , População Urbana , Adulto Jovem
14.
Crit Care Med ; 45(11): 1837-1844, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28841632

RESUMO

OBJECTIVES: Catatonia, a condition characterized by motor, behavioral, and emotional changes, can occur during critical illness and appear as clinically similar to delirium, yet its management differs from delirium. Traditional criteria for medical catatonia preclude its diagnosis in delirium. Our objective in this investigation was to understand the overlap and relationship between delirium and catatonia in ICU patients and determine diagnostic thresholds for catatonia. DESIGN: Convenience cohort, nested within two ongoing randomized trials. SETTING: Single academic medical center in Nashville, TN. PATIENTS: We enrolled 136 critically ill patients on mechanical ventilation and/or vasopressors, randomized to two usual care sedation regimens. MEASUREMENTS AND MAIN RESULTS: Patients were assessed for delirium and catatonia by independent and masked personnel using Confusion Assessment Method for the ICU and the Bush Francis Catatonia Rating Scale mapped to Diagnostic Statistical Manual 5 criterion A for catatonia. Of 136 patients, 58 patients (43%) had only delirium, four (3%) had only catatonia, 42 (31%) had both, and 32 (24%) had neither. In a logistic regression model, more catatonia signs were associated with greater odds of having delirium. For example, patient assessments with greater than or equal to three Diagnostic Statistical Manual 5 symptoms (75th percentile) had, on average, 27.8 times the odds (interquartile range, 12.7-60.6) of having delirium compared with patient assessments with zero Diagnostic Statistical Manual 5 criteria (25th percentile) present (p < 0.001). A cut-off of greater than or equal to 4 Bush Francis Catatonia Screening Instrument items was both sensitive (91%; 95% CI, 82.9-95.3) and specific (91%; 95% CI, 87.6-92.9) for Diagnostic Statistical Manual 5 catatonia. CONCLUSIONS: Given that about one in three patients had both catatonia and delirium, these data prompt reconsideration of Diagnostic Statistical Manual 5 criteria for "Catatonic Disorder Due to Another Medical Condition" that preclude diagnosing catatonia in the presence of delirium.


Assuntos
Catatonia/diagnóstico , Catatonia/epidemiologia , Estado Terminal , Delírio/diagnóstico por imagem , Delírio/epidemiologia , Idoso , Feminino , Humanos , Unidades de Terapia Intensiva/estatística & dados numéricos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Reprodutibilidade dos Testes , Respiração Artificial/métodos , Índice de Gravidade de Doença , Vasoconstritores/administração & dosagem
15.
Nature ; 476(7360): 316-9, 2011 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-21796117

RESUMO

Large outpourings of basaltic lava have punctuated geological time, but the mechanisms responsible for the generation of such extraordinary volumes of melt are not well known. Recent geochemical evidence suggests that an early-formed reservoir may have survived in the Earth's mantle for about 4.5 billion years (ref. 2), and melts of this reservoir contributed to the flood basalt emplaced on Baffin Island about 60 million years ago. However, the volume of this ancient mantle domain and whether it has contributed to other flood basalts is not known. Here we show that basalts from the largest volcanic event in geologic history--the Ontong Java plateau--also exhibit the isotopic and trace element signatures proposed for the early-Earth reservoir. Together with the Ontong Java plateau, we suggest that six of the largest volcanic events that erupted in the past 250 million years derive from the oldest terrestrial mantle reservoir. The association of these large volcanic events with an ancient primitive mantle source suggests that its unique geochemical characteristics--it is both hotter (it has greater abundances of the radioactive heat-producing elements) and more fertile than depleted mantle reservoirs-may strongly affect the generation of flood basalts.

16.
Nature ; 477(7362): 70-2, 2011 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-21849974

RESUMO

Chemical evolution of planetary bodies, ranging from asteroids to the large rocky planets, is thought to begin with differentiation through solidification of magma oceans many hundreds of kilometres in depth. The Earth's Moon is the archetypical example of this type of differentiation. Evidence for a lunar magma ocean is derived largely from the widespread distribution, compositional and mineralogical characteristics, and ancient ages inferred for the ferroan anorthosite (FAN) suite of lunar crustal rocks. The FANs are considered to be primary lunar flotation-cumulate crust that crystallized in the latter stages of magma ocean solidification. According to this theory, FANs represent the oldest lunar crustal rock type. Attempts to date this rock suite have yielded ambiguous results, however, because individual isochron measurements are typically incompatible with the geochemical make-up of the samples, and have not been confirmed by additional isotopic systems. By making improvements to the standard isotopic techniques, we report here the age of crystallization of FAN 60025 using the (207)Pb-(206)Pb, (147)Sm-(143)Nd and (146)Sm-(142)Nd isotopic systems to be 4,360 ± 3 million years. This extraordinarily young age requires that either the Moon solidified significantly later than most previous estimates or the long-held assumption that FANs are flotation cumulates of a primordial magma ocean is incorrect. If the latter is correct, then much of the lunar crust may have been produced by non-magma-ocean processes, such as serial magmatism.

17.
Nature ; 520(7547): 299-300, 2015 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-25877198
18.
Nature ; 466(7308): 853-6, 2010 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-20703304

RESUMO

Helium is a powerful tracer of primitive material in Earth's mantle. Extremely high (3)He/(4)He ratios in some ocean-island basalts suggest the presence of relatively undegassed and undifferentiated material preserved in Earth's mantle. However, terrestrial lavas with high (3)He/(4)He ratios have never been observed to host the primitive lead-isotopic compositions that are required for an early (roughly 4.5 Gyr ago) formation age. Here we show that Cenozoic-era Baffin Island and West Greenland lavas, previously found to host the highest terrestrial-mantle (3)He/(4)He ratios, exhibit primitive lead-isotope ratios that are consistent with an ancient mantle source age of 4.55-4.45 Gyr. The Baffin Island and West Greenland lavas also exhibit (143)Nd/(144)Nd ratios similar to values recently proposed for an early-formed (roughly 4.5 Gyr ago) terrestrial mantle reservoir. The combined helium-, lead- and Nd-isotopic compositions in Baffin Island and West Greenland lavas therefore suggest that their source is the most ancient accessible reservoir in the Earth's mantle, and it may be parental to all mantle reservoirs that give rise to modern volcanism.

20.
Plants (Basel) ; 13(2)2024 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-38256767

RESUMO

The aromatic compound (E)-anethol is widely used in the flavor, fragrance, and medicinal industries. This compound is commonly produced through steam distillation of fennel, star anise, and anise seed. Given the cost of production, these natural and authentic essential oils are commonly adulterated with lower-cost natural materials or synthetic alternatives. The current study investigates essential oil profiles (gas chromatography/mass spectrometry) and stable isotope ratios (gas chromatography/isotope ratio mass spectrometry) of the abundant compound (E)-anethol in both authentic reference standards (n = 15) and commercially available samples (n = 30). This multifaceted analytical approach establishes techniques for ensuring the authenticity of essential oil sources of (E)-anethol and was then used to evaluate the current essential oil market sources of (E)-anethol. These findings report that adulteration of (E)-anethol-containing natural products takes various forms, and a multifaceted analytical approach is recommended for authentication. Of the commercial samples analyzed for this report, 27% were adulterated.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA