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The abundances of (92)Nb and (146)Sm in the early solar system are determined from meteoritic analysis, and their stellar production is attributed to the p process. We investigate if their origin from thermonuclear supernovae deriving from the explosion of white dwarfs with mass above the Chandrasekhar limit is in agreement with the abundance of (53)Mn, another radionuclide present in the early solar system and produced in the same events. A consistent solution for (92)Nb and (53)Mn cannot be found within the current uncertainties and requires the (92)Nb/(92)Mo ratio in the early solar system to be at least 50% lower than the current nominal value, which is outside its present error bars. A different solution is to invoke another production site for (92)Nb, which we find in the α-rich freezeout during core-collapse supernovae from massive stars. Whichever scenario we consider, we find that a relatively long time interval of at least â¼ 10 My must have elapsed from when the star-forming region where the Sun was born was isolated from the interstellar medium and the birth of the Sun. This is in agreement with results obtained from radionuclides heavier than iron produced by neutron captures and lends further support to the idea that the Sun was born in a massive star-forming region together with many thousands of stellar siblings.
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Our focus of attention naturally fluctuates between different sources of information even when we desire to focus on a single object. Focused attention (FA) meditation is associated with greater control over this process, yet the neuronal mechanisms underlying this ability are not entirely understood. Here, we hypothesize that the capacity of attention to transiently focus and swiftly change relates to the critical dynamics emerging when neuronal systems balance at a point of instability between order and disorder. In FA meditation, however, the ability to stay focused is trained, which may be associated with a more homogeneous brain state. To test this hypothesis, we applied analytical tools from criticality theory to EEG in meditation practitioners and meditation-naïve participants from two independent labs. We show that in practitioners-but not in controls-FA meditation strongly suppressed long-range temporal correlations (LRTC) of neuronal oscillations relative to eyes-closed rest with remarkable consistency across frequency bands and scalp locations. The ability to reduce LRTC during meditation increased after one year of additional training and was associated with the subjective experience of fully engaging one's attentional resources, also known as absorption. Sustained practice also affected normal waking brain dynamics as reflected in increased LRTC during an eyes-closed rest state, indicating that brain dynamics are altered beyond the meditative state. Taken together, our findings suggest that the framework of critical brain dynamics is promising for understanding neuronal mechanisms of meditative states and, specifically, we have identified a clear electrophysiological correlate of the FA meditation state.
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Atención/fisiología , Ondas Encefálicas/fisiología , Encéfalo/fisiología , Meditación , Adulto , Estudios de Cohortes , Emociones/fisiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Práctica Psicológica , Descanso , Procesamiento de Señales Asistido por Computador , Pensamiento/fisiología , Factores de Tiempo , Adulto JovenRESUMEN
Almost a decade after methane was first reported in the atmosphere of Mars there is an intensive discussion about both the reliability of the observations--particularly the suggested seasonal and latitudinal variations--and the sources of methane on Mars. Given that the lifetime of methane in the Martian atmosphere is limited, a process on or below the planet's surface would need to be continuously producing methane. A biological source would provide support for the potential existence of life on Mars, whereas a chemical origin would imply that there are unexpected geological processes. Methane release from carbonaceous meteorites associated with ablation during atmospheric entry is considered negligible. Here we show that methane is produced in much larger quantities from the Murchison meteorite (a type CM2 carbonaceous chondrite) when exposed to ultraviolet radiation under conditions similar to those expected at the Martian surface. Meteorites containing several per cent of intact organic matter reach the Martian surface at high rates, and our experiments suggest that a significant fraction of the organic matter accessible to ultraviolet radiation is converted to methane. Ultraviolet-radiation-induced methane formation from meteorites could explain a substantial fraction of the most recently estimated atmospheric methane mixing ratios. Stable hydrogen isotope analysis unambiguously confirms that the methane released from Murchison is of extraterrestrial origin. The stable carbon isotope composition, in contrast, is similar to that of terrestrial microbial origin; hence, measurements of this signature in future Mars missions may not enable an unambiguous identification of biogenic methane.
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Atmósfera/química , Medio Ambiente Extraterrestre/química , Marte , Meteoroides , Metano/química , Metano/efectos de la radiación , Rayos Ultravioleta , Exobiología , Hawaii , Pectinas/química , Presión , Suelo/química , TemperaturaRESUMEN
We report a systematic spectroscopical investigation of three plagioclase particles (RB-QD04-0022, RA-QD02-0025-01, and RA-QD02-0025-02) returned by the Hayabusa spacecraft from the asteroid Itokawa, by means of scanning electron microscopy, cathodoluminescence microscopy/spectroscopy, and micro-Raman spectroscopy. The cathodoluminescence properties are used to evaluate the crystallization effects and the degree of space weathering processes, especially the shock-wave history of Itokawa. They provide new insights regarding spectral changes of asteroidal bodies due to space weathering processes. The cathodoluminescence spectra of the plagioclase particles from Itokawa show a defect-related broad band centered at around 450 nm, with a shoulder peak at 425 nm in the blue region, but there are no Mn- or Fe-related emission peaks. The absence of these crystal field-related activators indicates that the plagioclase was formed during thermal metamorphism at subsolidus temperature and extreme low oxygen fugacity. Luminescence characteristics of the selected samples do not show any signatures of the shock-induced microstructures or amorphization, indicating that these plagioclase samples suffered no (or low-shock pressure regime) shock metamorphism. Cathodoluminescence can play a key role as a powerful tool to determine mineralogy of fine-grained astromaterials.
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Pain can be modulated by several cognitive techniques, typically involving increased cognitive control and decreased sensory processing. Recently, it has been demonstrated that pain can also be attenuated by mindfulness. Here, we investigate the underlying brain mechanisms by which the state of mindfulness reduces pain. Mindfulness practitioners and controls received unpleasant electric stimuli in the functional magnetic resonance imaging scanner during a mindfulness and a control condition. Mindfulness practitioners, but not controls, were able to reduce pain unpleasantness by 22% and anticipatory anxiety by 29% during a mindful state. In the brain, this reduction was associated with decreased activation in the lateral prefrontal cortex and increased activation in the right posterior insula during stimulation and increased rostral anterior cingulate cortex activation during the anticipation of pain. These findings reveal a unique mechanism of pain modulation, comprising increased sensory processing and decreased cognitive control, and are in sharp contrast to established pain modulation mechanisms.
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Encéfalo/fisiopatología , Cognición/fisiología , Curación Mental/psicología , Manejo del Dolor/métodos , Dolor/fisiopatología , Sensación/fisiología , Adulto , Anticipación Psicológica/fisiología , Ansiedad/psicología , Conducta/fisiología , Corteza Cerebral/fisiopatología , Interpretación Estadística de Datos , Imagen Eco-Planar , Terapia por Estimulación Eléctrica , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Imagen por Resonancia Magnética , Masculino , Manejo del Dolor/efectos adversos , Manejo del Dolor/psicología , Dimensión del Dolor , Corteza Prefrontal/fisiopatología , Corteza Somatosensorial/fisiopatología , Tálamo/fisiopatologíaRESUMEN
Color centers in selected micro- and nanodiamond samples were investigated by cathodoluminescence (CL) microscopy and spectroscopy at 298 K [room temperature (RT)] and 77 K [liquid-nitrogen temperature (LNT)] to assess the value of the technique for astrophysics. Nanodiamonds from meteorites were compared with synthetic diamonds made with different processes involving distinct synthesis mechanisms (chemical vapor deposition, static high pressure high temperature, detonation). A CL emission peak centered at around 540 nm at 77 K was observed in almost all of the selected diamond samples and is assigned to the dislocation defect with nitrogen atoms. Additional peaks were identified at 387 and 452 nm, which are related to the vacancy defect. In general, peak intensity at LNT at the samples was increased in comparison to RT. The results indicate a clear temperature-dependence of the spectroscopic properties of diamond. This suggests the method is a useful tool in laboratory astrophysics.
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The abundance and distribution of water within Mars through time plays a fundamental role in constraining its geological evolution and habitability. The isotopic composition of martian hydrogen provides insights into the interplay between different water reservoirs on Mars. However, D/H (deuterium/hydrogen) ratios of martian rocks and of the martian atmosphere span a wide range of values. This has complicated identification of distinct water reservoirs in and on Mars within the confines of existing models that assume an isotopically homogenous mantle. Here we present D/H data collected by secondary ion mass spectrometry for two martian meteorites. These data indicate that the martian crust has been characterized by a constant D/H ratio over the last 3.9 billion years. The crust represents a reservoir with a D/H ratio that is intermediate between at least two isotopically distinct primordial water reservoirs within the martian mantle, sampled by partial melts from geochemically depleted and enriched mantle sources. From mixing calculations, we find that a subset of depleted martian basalts are consistent with isotopically light hydrogen (low D/H) in their mantle source, whereas enriched shergottites sampled a mantle source containing heavy hydrogen (high D/H). We propose that the martian mantle is chemically heterogeneous with multiple water reservoirs, indicating poor mixing within the mantle after accretion, differentiation, and its subsequent thermochemical evolution.
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Research on meditation is advancing, but few studies about the motivations of meditators exist. Additionally, many forms and traditions of meditation have yet to be investigated. This study addresses both of these issues by presenting an overview of different forms of motivations found in contemporary Anthroposophic meditation practice. 30 Anthroposophic meditators were interviewed about their meditation experiences. The interviews were examined using thematic analysis. 14 data-driven themes were extracted and organized within a framework consisting of three superordinate theory-driven forms of motivation: External, internal and service. A developmental trajectory running from external and internal to service motivations is indicated. This approach improves upon a scheme developed by Shapiro by including additional types of motivations and being able to differentiate between forms of motivations that are fundamentally different: Self-related (heteronomous and autonomous) motivations and other-related motivations.
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Medicina Antroposófica , Personal de Salud/psicología , Meditación/psicología , Motivación , Actitud del Personal de Salud , Femenino , Humanos , Masculino , Persona de Mediana Edad , Investigación CualitativaRESUMEN
Goal: We aimed to identify electroencephalographic (EEG) signal fluctuations within independent components (ICs) that correlate to spontaneous blood oxygenation level dependent (BOLD) activity in regions of the default mode network (DMN) during eyes-closed resting state. Methods: We analyzed simultaneously acquired EEG and functional magnetic resonance imaging (fMRI) eyes-closed resting state data in a convenience sample of 30 participants. IC analysis (ICA) was used to decompose the EEG time-series and common ICs were identified using data-driven IC clustering across subjects. The IC time courses were filtered into seven frequency bands, convolved with a hemeodynamic response function (HRF) and used to model spontaneous fMRI signal fluctuations across the brain. In parallel, group ICA analysis was used to decompose the fMRI signal into ICs from which the DMN was identified. Frequency and IC cluster associated hemeodynamic correlation maps obtained from the regression analysis were spatially correlated with the DMN. To investigate the reliability of our findings, the analyses were repeated with data collected from the same subjects 1 year later. Results: Our results indicate a relationship between power fluctuations in the delta, theta, beta and gamma frequency range and the DMN in different EEG ICs in our sample as shown by small to moderate spatial correlations at the first measurement (0.234 < |r| < 0.346, p < 0.0001). Furthermore, activity within an EEG component commonly identified as eye movements correlates with BOLD activity within regions of the DMN. In addition, we demonstrate that correlations between EEG ICs and the BOLD signal during rest are in part stable across time. Discussion: We show that ICA source separated EEG signals can be used to investigate electrophysiological correlates of the DMN. The relationship between the eye movement component and the DMN points to a behavioral association between DMN activity and the level of eye movement or the presence of neuronal activity in this component. Previous findings of an association between frontal midline theta activity and the DMN were replicated.
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This study investigated differences in brain activation during meditation between meditators and non-meditators. Fifteen Vipassana meditators (mean practice: 7.9 years, 2h daily) and fifteen non-meditators, matched for sex, age, education, and handedness, participated in a block-design fMRI study that included mindfulness of breathing and mental arithmetic conditions. For the meditation condition (contrasted to arithmetic), meditators showed stronger activations in the rostral anterior cingulate cortex and the dorsal medial prefrontal cortex bilaterally, compared to controls. Greater rostral anterior cingulate cortex activation in meditators may reflect stronger processing of distracting events. The increased activation in the medial prefrontal cortex may reflect that meditators are stronger engaged in emotional processing.
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Mapeo Encefálico , Lóbulo Frontal/fisiología , Giro del Cíngulo/fisiología , Meditación , Procesos Mentales/fisiología , Adulto , Estudios de Casos y Controles , Femenino , Lóbulo Frontal/irrigación sanguínea , Lateralidad Funcional/fisiología , Giro del Cíngulo/irrigación sanguínea , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Imagen por Resonancia Magnética/métodos , Masculino , Matemática , Oxígeno/sangreRESUMEN
The article reviews the current knowledge regarding altered states of consciousness (ASC) (a) occurring spontaneously, (b) evoked by physical and physiological stimulation, (c) induced by psychological means, and (d) caused by diseases. The emphasis is laid on psychological and neurobiological approaches. The phenomenological analysis of the multiple ASC resulted in 4 dimensions by which they can be characterized: activation, awareness span, self-awareness, and sensory dynamics. The neurophysiological approach revealed that the different states of consciousness are mainly brought about by a compromised brain structure, transient changes in brain dynamics (disconnectivity), and neurochemical and metabolic processes. Besides these severe alterations, environmental stimuli, mental practices, and techniques of self-control can also temporarily alter brain functioning and conscious experience.
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Encéfalo/diagnóstico por imagen , Encéfalo/fisiología , Trastornos de la Conciencia , Nivel de Alerta/fisiología , Dieta , Sueños/fisiología , Electroencefalografía , Humanos , Tomografía de Emisión de Positrones , Sueño/fisiología , InaniciónRESUMEN
The aim of this fMRI study was to explore brain structures that are involved in the processing of erotic and disgust-inducing pictures. The stimuli were chosen to trigger approach and withdrawal tendencies, respectively. By adding sadomasochistic (SM) scenes to the design and examining 12 subjects with and 12 subjects without sadomasochistic preferences, we introduced a picture category that induced erotic pleasure in one sample and disgust in the other sample. Since we also presented neutral pictures, all subjects viewed pictures of four different categories: neutral, disgust-inducing, erotic, and SM erotic pictures. The analysis indicated that several brain structures are commonly involved in the processing of disgust-inducing and erotic pictures (occipital cortex, hippocampus, thalamus, and the amygdala). The ventral striatum was specifically activated when subjects saw highly sexually arousing pictures. This indicates the involvement of the human reward system during the processing of visual erotica.
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Afecto , Encéfalo/irrigación sanguínea , Literatura Erótica , Estimulación Luminosa , Adulto , Amígdala del Cerebelo/irrigación sanguínea , Amígdala del Cerebelo/metabolismo , Ganglios Basales/irrigación sanguínea , Ganglios Basales/metabolismo , Encéfalo/metabolismo , Femenino , Lateralidad Funcional/fisiología , Hemodinámica/fisiología , Hipocampo/irrigación sanguínea , Hipocampo/metabolismo , Humanos , Imagen por Resonancia Magnética , Masculino , Lóbulo Occipital/irrigación sanguínea , Lóbulo Occipital/metabolismo , Personalidad , Inventario de Personalidad , Recompensa , Conducta Sexual/fisiología , Tálamo/irrigación sanguínea , Tálamo/metabolismoRESUMEN
Although research on the effects of mindfulness meditation (MM) is increasing, still very little has been done to address its influence on the white matter (WM) of the brain. We hypothesized that the practice of MM might affect the WM microstructure adjacent to five brain regions of interest associated with mindfulness. Diffusion tensor imaging was employed on samples of meditators and non-meditators (n = 64) in order to investigate the effects of MM on group difference and aging. Tract-Based Spatial Statistics was used to estimate the fractional anisotrophy of the WM connected to the thalamus, insula, amygdala, hippocampus, and anterior cingulate cortex. The subsequent generalized linear model analysis revealed group differences and a group-by-age interaction in all five selected regions. These data provide preliminary indications that the practice of MM might result in WM connectivity change and might provide evidence on its ability to help diminish age-related WM degeneration in key regions which participate in processes of mindfulness.
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The majority of neuroimaging studies on affective processing have indicated that there are specific brain structures, which are selectively responsive to fear and disgust. Whereas the amygdala is assumed to be fear-related, the insular cortex is most likely involved in disgust processing. Since these findings are mainly a result of studies focusing exclusively either on fear, or on disgust, but rarely on both emotions together, the present experiment explored the neural effects of viewing disgusting and fear-inducing pictures in contrast to neutral pictures. This was done by means of functional magnetic resonance imaging (fMRI) with 19 subjects (nine males, ten females), who also gave affective ratings for the presented pictures. The fear and the disgust pictures were able to induce the target emotions and they received comparable valence and arousal ratings. The processing of both aversive picture types was associated with an increased brain activation in the occipital-temporal lobe, in the prefrontal cortex, and in the thalamus. The amygdala was significantly activated by disgusting, but not by fear-inducing, pictures. Thus, our data are in contrast with the idea of highly emotion-specific brain structures and rather suggest the existence of a common affective circuit.
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Emociones/fisiología , Miedo/fisiología , Hemodinámica/fisiología , Adulto , Encéfalo/fisiología , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Imagen por Resonancia Magnética , Masculino , Oxígeno/sangre , Estimulación Luminosa , Caracteres SexualesRESUMEN
Controversy continues as to whether chloromethane (CH3Cl) detected during pyrolysis of Martian soils by the Viking and Curiosity Mars landers is indicative of organic matter indigenous to Mars. Here we demonstrate CH3Cl release (up to 8â µg/g) during low temperature (150-400°C) pyrolysis of the carbonaceous chondrite Murchison with chloride or perchlorate as chlorine source and confirm unequivocally by stable isotope analysis the extraterrestrial origin of the methyl group (δ(2)H +800 to +1100, δ(13)C -19.2 to +10,). In the terrestrial environment CH3Cl released during pyrolysis of organic matter derives from the methoxyl pool. The methoxyl pool in Murchison is consistent both in magnitude (0.044%) and isotope signature (δ(2)H +1054 ± 626, δ(13)C +43.2 ± 38.8,) with that of the CH3Cl released on pyrolysis. Thus CH3Cl emissions recorded by Mars lander experiments may be attributed to methoxyl groups in undegraded organic matter in meteoritic debris reaching the Martian surface being converted to CH3Cl with perchlorate or chloride in Martian soil. However we cannot discount emissions arising additionally from organic matter of indigenous origin. The stable isotope signatures of CH3Cl detected on Mars could potentially be utilized to determine its origin by distinguishing between terrestrial contamination, meteoritic infall and indigenous Martian sources.
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Among the short-lived radioactive nuclei inferred to be present in the early solar system via meteoritic analyses, there are several heavier than iron whose stellar origin has been poorly understood. In particular, the abundances inferred for (182)Hf (half-life = 8.9 million years) and (129)I (half-life = 15.7 million years) are in disagreement with each other if both nuclei are produced by the rapid neutron-capture process. Here, we demonstrate that contrary to previous assumption, the slow neutron-capture process in asymptotic giant branch stars produces (182)Hf. This has allowed us to date the last rapid and slow neutron-capture events that contaminated the solar system material at ~100 million years and ~30 million years, respectively, before the formation of the Sun.
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Many studies investigating music processing in adult musicians and nonmusicians point towards pronounced behavioral and neurophysiological differences between the two groups. Recent studies indicate that these differences can already be found in early childhood. Further, electro-encephalography studies using musical discrimination tasks have demonstrated that differences in music processing become more pronounced when explicitly rather than implicitly trained musical abilities are required. Exploring the functional neuroanatomy underlying the processing of different expectation violations in children and its association with musical training, we investigated neural responses to different melodic deviances in musically trained and untrained children. Using functional magnetic resonance imaging, children (aged 11-14 years) were examined while comparing pairs of short melodies that were either identical or differed with respect to four notes. The implemented deviances were either subtle (by inserting plausible in-key notes) or obvious (by inserting implausible out-of-key notes). Our results indicate a strong association between musical training and functional neuroanatomy of the brain. Similar to research on music processing in adults, the processing of obvious melodic deviances activated a network involving inferior frontal, premotor and anterior insula regions in musically trained and untrained children. By contrast, subtle deviances led to activation in the inferior frontal and premotor cortex, the anterior insula, the superior temporal gyrus, and the supramarginal gyrus in musically trained children only. Our work provides further insights into the functional neuroanatomy of melody processing and its association with musical training in children, providing the basis for further studies specifying distinct musical processes (e.g. contour and interval processing).
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Vías Auditivas/crecimiento & desarrollo , Percepción Auditiva/fisiología , Aprendizaje/fisiología , Música/psicología , Red Nerviosa/crecimiento & desarrollo , Adolescente , Vías Auditivas/anatomía & histología , Vías Auditivas/fisiología , Niño , Femenino , Humanos , Masculino , Red Nerviosa/fisiologíaRESUMEN
Cultivation of mindfulness, the nonjudgmental awareness of experiences in the present moment, produces beneficial effects on well-being and ameliorates psychiatric and stress-related symptoms. Mindfulness meditation has therefore increasingly been incorporated into psychotherapeutic interventions. Although the number of publications in the field has sharply increased over the last two decades, there is a paucity of theoretical reviews that integrate the existing literature into a comprehensive theoretical framework. In this article, we explore several components through which mindfulness meditation exerts its effects: (a) attention regulation, (b) body awareness, (c) emotion regulation (including reappraisal and exposure, extinction, and reconsolidation), and (d) change in perspective on the self. Recent empirical research, including practitioners' self-reports and experimental data, provides evidence supporting these mechanisms. Functional and structural neuroimaging studies have begun to explore the neuroscientific processes underlying these components. Evidence suggests that mindfulness practice is associated with neuroplastic changes in the anterior cingulate cortex, insula, temporo-parietal junction, fronto-limbic network, and default mode network structures. The authors suggest that the mechanisms described here work synergistically, establishing a process of enhanced self-regulation. Differentiating between these components seems useful to guide future basic research and to specifically target areas of development in the treatment of psychological disorders.
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Mindfulness meditators practice the non-judgmental observation of the ongoing stream of internal experiences as they arise. Using voxel-based morphometry, this study investigated MRI brain images of 20 mindfulness (Vipassana) meditators (mean practice 8.6 years; 2 h daily) and compared the regional gray matter concentration to that of non-meditators matched for sex, age, education and handedness. Meditators were predicted to show greater gray matter concentration in regions that are typically activated during meditation. Results confirmed greater gray matter concentration for meditators in the right anterior insula, which is involved in interoceptive awareness. This group difference presumably reflects the training of bodily awareness during mindfulness meditation. Furthermore, meditators had greater gray matter concentration in the left inferior temporal gyrus and right hippocampus. Both regions have previously been found to be involved in meditation. The mean value of gray matter concentration in the left inferior temporal gyrus was predictable by the amount of meditation training, corroborating the assumption of a causal impact of meditation training on gray matter concentration in this region. Results suggest that meditation practice is associated with structural differences in regions that are typically activated during meditation and in regions that are relevant for the task of meditation.
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Concienciación/fisiología , Mapeo Encefálico , Encéfalo/fisiología , Lateralidad Funcional/fisiología , Meditación , Adulto , Atención/fisiología , Encéfalo/anatomía & histología , Potenciales Evocados/fisiología , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Análisis por Apareamiento , Tamaño de los ÓrganosRESUMEN
Current models of attention describe attention not as a homogenous entity but as a set of neural networks whose measurement yields a set of three endophenotypes-alerting, orienting, and executive control. Previous findings revealed different neuroanatomical regions for these subsystems, and data from twin studies indicate differences in their heritability. The present study investigated the molecular genetic basis of attention in a sample of 100 healthy subjects. Attention performance was assessed with the attention network test that distinguishes alerting, orienting, and executive control (conflict) using a simple reaction time paradigm with different cues and congruent and incongruent flankers. Two gene loci on candidate genes for cognitive functioning, the functional catechol-O-methyltransferase (COMT) VAL158MET and the tryptophan hydroxylase 2 (TPH2) -703 G/T promoter polymorphism, were tested for possible associations with attention. COMT is involved in the catabolism of dopamine, and TPH is the rate-limiting enzyme for serotonin synthesis. Results showed no effect of the COMT polymorphism on attention performance. However, the TT genotype of TPH2 -03 G/T was significantly associated with more errors (a possible indicator of impaired impulse control; p = .001) and with decreased performance in executive control (p = .001). This single-nucleotide polymorphism on the TPH2 gene explained more than 10% of the variance in both indicators of attention stressing the role of the serotonergic system for cognitive functions.