Abrupt Termination Research Articles

Multi-band Polarimetry of the Lunar Surface. III. Polarization Phase Curve

Polarimetry of the Moon reveals characteristics of the lunar regolith such as the size and composition of regolith grains, which are useful in understanding the surface properties and to determine landing sites for future lunar missions. As part of the Korea Pathfinder Lunar Orbiter (KPLO) mission, the wide-angle polarimetric camera (PolCam) will perform polarimetric measurements of the Moon for the first time from the lunar orbit. Because the degree of linear polarization is a function of the phase angle, it is necessary to observe the same region multiple times at various phase angles to construct the phase curve of polarization and derive the map of maximum polarization (Pmax). Any unexpected discontinuities of observing runs or an abrupt termination of the mission may cause the scientific goals of the PolCam to be unachievable. Here, we investigated how to recover the polarimetric phase curve when the observational data set is incomplete. Using ground-based polarimetry data, we explored the parameter space of the fitting formula of the phase curve and show that the formula can be reduced into a single parameter form. Assuming several cases of incomplete measurements, we constructed Pmax maps and investigated the allowable range of the phase-angle coverage. We show that Pmax can be estimated with a root-mean-square discrepancy less than 0.5%p when the maximum phase angle covered is greater than 90°.

Outcrop analysis and facies model of an Upper Permian tidally influenced fluvio-deltaic system: Northern Sydney Basin, SE Australia

AbstractAn integrated study of sedimentological, sequence-stratigraphic and palaeodispersal analysis was applied to the Upper-Permian clastic sedimentary succession in the Northern Sydney Basin, Australia. The succession is subdivided into fifteen facies and three facies associations. The facies associations are further subdivided into eight sub-facies associations. The sedimentary evolution involves progradation from delta-front to delta-plain to fluvial depositional environments, with a significant increase in sediment grain size across the unconformable contact that separates the deltaic from the overlying fluvial system. In contrast to the delta front that is wave/storm- and/or river-influenced, the delta plain is significantly affected by tides, with the impact of tidal currents decreasing up-sequence in the delta plain. The general lack of wave-influenced sedimentary structures suggests low wave energy in the delta plain. The abrupt termination of the tidal impact in the fluvial realm relates to the steep topographic gradients and high sediment supply, which accompanied the uplift of the New England Orogen. The sequence-stratigraphic framework includes highstand (deltaic forest and topset) and lowstand (fluvial topset) systems tracts, separated by a subaerial unconformity. In contrast to most of the mud-rich modern counterparts, this is an example of a sand-rich tidally influenced deltaic system, developed adjacent to the source region. This investigation presents a depositional model for tidal successions in regions of tectonic uplift and confinement.

Linkage of crustal deformation between the Archaean basement and the Proterozoic cover in the Peräpohja Area, northern Fennoscandia

Reconstructed variations in stratigraphic thicknesses combined with mapped variations in fold-and-thrust belt structural styles and patterns of the entire Palaeoproterozoic Peräpohja Belt in northern Finland show that both the deposition of the 2.4–1.9 Ga supracrustal rocks and the structural evolution during the subsequent Svecofennian Orogeny (1.9–1.8 Ga) have been tightly controlled by (i) the palaeo-topography of the Archaean (>2.5 Ga) basement, and (ii) the reactivation of Archaean basement faults during the multiple stages of rifting and deposition of the supracrustals, as well as during subsequent basin inversion and fold-and-thrust belt development. Folds and thrusts in the supracrustal sequence are found to be largely detached from the underlying basement along the Petäjäskoski Detachment Zone (PDZ) that formed within a mechanically weak stratigraphic unit in the basal part of the Peräpohja Belt stratigraphy. The pattern of contractional structures is complex, but developed during one phase of simple, progressive south-vergent thrusting. Two styles of basement-cover linkage are recognised: The hard-linked style is best illustrated by the reverse Sihtuuna Fault currently defining the northern margin of the E-W to ENE-WSW trending basement horsts and the overlying anticlines, and juxtaposing the stratigraphically lowermost Peräpohja Belt rocks with higher-up stratigraphy, indicating the fault is inherited after a pre-existing basement structure. Based on the distribution and thickness variation of the Palaeoproterozoic supracrustal units, the faults bounding the basement horst were active as extensional faults during deposition. The soft-linked style relationship is evident as abrupt terminations of thrust-related elongate domes and localisation of the compressional overprint into the NW-SE trending central graben. Understanding the basement architecture and basement-cover linkages is highly significant because the majority of the known mineralizations of the belt are located along or close to the basement faults.

Managing Antidepressant Discontinuation: A Systematic Review.

We aimed to determine the effectiveness of interventions to manage antidepressant discontinuation, and the outcomes for patients. We conducted a systematic review with narrative synthesis and meta-analysis of studies published to March 2017. Studies were eligible for inclusion if they were randomized controlled trials, quasi-experimental studies, or observational studies assessing interventions to facilitate discontinuation of antidepressants for depression in adults. Our primary outcomes were antidepressant discontinuation and discontinuation symptoms. Secondary outcomes were relapse/recurrence; quality of life; antidepressant reduction; and sexual, social, and occupational function. Of 15 included studies, 12 studies (8 randomized controlled trials, 2 single-arm trials, 2 retrospective cohort studies) were included in the synthesis. None were rated as having high risk for selection or detection bias. Two studies prompting primary care clinician discontinuation with antidepressant tapering guidance found 6% and 7% of patients discontinued, vs 8% for usual care. Six studies of psychological or psychiatric treatment plus tapering reported cessation rates of 40% to 95%. Two studies reported a higher risk of discontinuation symptoms with abrupt termination. At 2 years, risk of relapse/recurrence was lower with cognitive behavioral therapy plus taper vs clinical management plus taper (15% to 25% vs 35% to 80%: risk ratio = 0.34; 95% CI, 0.18-0.67; 2 studies). Relapse/recurrence rates were similar for mindfulness-based cognitive therapy with tapering and maintenance antidepressants (44% to 48% vs 47% to 60%; 2 studies). Cognitive behavioral therapy or mindfulness-based cognitive therapy can help patients discontinue antidepressants without increasing the risk of relapse/recurrence, but are resource intensive. More scalable interventions incorporating psychological support are needed.

Fast Charging of Li-Ion Cells: Part III. Relaxation Dynamics and Trap-Controlled Lithium Ion Transport

Fast charging of Li-ion batteries would ease consumer concerns regarding refueling time of electric vehicles. In this series of articles, we are systematically examining the effects of high currents flowing through the cell. Here we consider open-circuit relaxation dynamics for cell voltage and individual electrode potentials after abrupt termination of steady-state charging currents (1-6C) or short current pulses (< 30 s) of either polarity (to 16C). We demonstrate that dispersive kinetics observed after these current perturbations become faster for higher currents applied before the rest period. Our observations indicate that the voltage relaxation behaviors (i) depend on the current during charge, and less so on the state of charge, (ii) display universal stretched-exponential kinetics, (iii) can be induced by a short current pulse, (iv) require a minimum amount of charge transfer during the pulse, and (v) originate mainly from the oxide cathode. Trap controlled Li+ ion transport through a partially disordered oxygen-depleted subsurface layer in the cathode is suggested as a possible origin for the relaxation behavior. The slow multidecadal responses to high currents can cause the nonlinearities observed during rapid charging of the electrochemical cells, reported in Part 2 of this series.

Patients With Obesity Exhibit a Plateau Pattern of the Right Ventricular Waveform.

BackgroundVentricular waveforms are characterized by a dip-and-plateau pattern during diastole owing to an abrupt termination of ventricular filling because of pericardial constraint under conditions such as constrictive pericarditis (CP). However, constrictive hemodynamics is not specifically caused by CP. Therefore, this study aimed to evaluate whether patients with obesity exhibited constrictive hemodynamics.MethodsOverall, 60 consecutive Japanese patients (mean age, 69.5 years; 45% women) who underwent right heart catheterization at the Japan Community Healthcare Organization Osaka Hospital from July 2016 to September 2018 were examined. Two-dimensional echocardiography was used to measure the epicardial adipose tissue (EAT) in the standard parasternal long-axis view during end-diastole. Because patients who underwent open-heart surgery were highly likely to have CP, they were excluded.ResultsAmong the 60 patients, 11 (18%) exhibited a plateau pattern of the right ventricular waveform and had a mean EAT value of 4.2 mm, which was significantly higher than that of patients without such a pattern (2.1 mm, P < 0.001). Similarly, the mean body mass index (BMI) values were significantly higher in patients with a plateau pattern than in those without it (27.2 vs. 21.8 kg/m2, P < 0.001). EAT was significantly correlated with the BMI (r = 0.72, P < 0.001). In patients with a plateau pattern, the triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) levels were significantly higher (TG: 150 vs. 100 mg/dL, LDL-C: 121 vs. 95 mg/dL, P < 0.05) and the left atrial diameter (52.8 vs. 44.7 mm, P < 0.01) and left atrial volume index (58.7 vs. 47.6 mL/m2, P < 0.05) were significantly greater than those in the patients without it. The EAT was also significantly correlated with the TG level (r = 0.37, P < 0.01).ConclusionsObese patients may present with constrictive hemodynamics, suggesting left ventricular diastolic dysfunction. EAT was significantly correlated with metabolic syndrome components, namely obesity and TG levels.

Acute motor and vocal response of humpback whales (Megaptera novaeangliae) to playback of amplitude-modulated noise: A method to test frequency range of hearing

The frequency hearing range of mysticete cetaceans remains elusive despite a growing concern about the negative impacts of anthropogenic noise. A playback study was conducted in the Maui Nui region of Hawaii during March 2018. Stationary humpback whales (i.e., single singers or silent dyads) were targeted due to their predictable behavior that allowed for observations pre, during, and post-playback. Playback consisted of amplitude-modulated noise that was broadband, high-pass filtered, or 1/3 octave bandpass filtered. The animal’s motor behavior was recorded by video from a swimmer positioned above the animal. Acoustic playback and acquisition was performed from a small vessel approximately 41 m to 56 m from a targeted animal. A total of 16 playbacks were conducted with estimated received levels between 116 dB–138 dB RMS (re 1 μPa). Motor responses ranged from abruptly swimming away to subtle fluke movements with a median response latency of 1.7 sec (n = 7). Vocal responses ranged from abrupt song termination to unexpected changes in song unit pattern, with a median response latency of 2.94 sec (n = 8). This novel playback methodology was effective at producing and measuring motor and vocal responses to sound and may be useful in measuring the hearing range of mysticetes.

Information carried by a surface-plasmon-polariton wave across a gap

Faster communication between electronic devices inside a semiconductor chip may be enabled by optical interconnects based on surface-plasmon-polariton (SPP) waves, as their high localization overcomes the size mismatch between optical and electronic devices. Hence, we solved the Maxwell equations in the time domain to investigate the jump of a pulse-modulated carrier SPP wave across a semi-infinite gap on the metallic side of a planar metal/dielectric interface. The Drude model was used for the susceptibility of the metal and the air was taken as the dielectric material in our calculations. The Pearson correlation coefficient of the appropriate component of the Poynting vector at two points on either side of the gap was calculated. After an abrupt termination of the metal, reflection was very low and the signal continued to propagate in air as a precursor followed by a somewhat distorted version of the launched pulse. Information encoded as the existence of a pulse was found to be strongly and positively correlated with the transmitted signal. When the metal/air interface was restored after a gap of width equal to the carrier wavelength in free space, the signal received across the gap still comprised a precursor and a main pulse that were still strongly and positively correlated with the transmitted signal. Thus, information continued to propagate in the forward direction for a long distance after the gap, a promising result for SPP-wave-based optical interconnects.

Memory, Mourning, and Writing: Abram Kardiner's Memoir of Freud.

This paper offers a reading of psychoanalyst Abram Kardiner's memoir, which tells the story of his analytic encounter with Freud in the early 1920s. The memoir describes Kardiner's dependence on caretakers, parents, and psychoanalysts, as well as painful separations that are understood in relation to his deprived childhood. These memories were revived in analysis and then reactivated in its abrupt termination. In retrospect, it can be seen that Kardiner's work of memory and mourning is tied in ambiguous ways to Freud's mourning over his daughter Sophie at the time. The present paper uses ideas on writing and translation by Derrida, Ricoeur, and Laplanche to suggest a comparative reading of the texts written by the analyst and the patient. This reading views the essence of autobiographical writing not only as a reconstruction of the past but also as a new translation, with an emphasis on the experience of loss.

Mild and Arid Climate in the Eastern Sahara‐Arabian Desert During the Late Little Ice Age

AbstractThe climate of the Sahara and Arabian Deserts during the Little Ice Age is not well known, due to a lack of annually resolved natural and documentary archives. We present an annual reconstruction of temperature and aridity derived from Sr/Ca and oxygen isotopes in a coral of the desert‐surrounded northern Red Sea. Our data indicate that the eastern Sahara and Arabian Deserts did not experience pronounced cooling during the late Little Ice Age (~1750–1850) but suggest an even more arid mean climate than in the following ~150 years. The mild temperatures are broadly in line with predominantly negative phases of the North Atlantic Oscillation during the Little Ice Age. The more arid climate is best explained by meridional advection of dry continental air from Eurasia. We find evidence for an abrupt termination of the more arid climate after 1850, coincident with a reorganization of the atmospheric circulation over Europe.

The continuous rise of bulges out of galactic disks

Context. A key subject in extragalactic astronomy concerns the chronology and driving mechanisms of bulge formation in late-type galaxies (LTGs). The standard scenario distinguishes between classical bulges and pseudo-bulges (CBs and PBs, respectively), the first thought to form monolithically prior to disks and the second gradually out of disks. These two bulge formation routes obviously yield antipodal predictions on the bulge age and bulge-to-disk age contrast, both expected to be high (low) in CBs (PBs). Aims. Our main goal is to explore whether bulges in present-day LTGs segregate into two evolutionary distinct classes, as expected from the standard scenario. Other questions motivating this study center on evolutionary relations between LTG bulges and their hosting disks, and the occurrence of accretion-powered nuclear activity as a function of bulge stellar mass ℳ⋆ and stellar surface density Σ⋆. Methods. In this study, we have combined three techniques – surface photometry, spectral modeling of integral field spectroscopy data and suppression of stellar populations younger than an adjustable age cutoff with the code REMOVEYOUNG (ℛ𝒴) – toward a systematic analysis of the physical and evolutionary properties (e.g., ℳ⋆, Σ⋆ and mass-weighted stellar age 〈t⋆〉ℳ and metallicity 〈Z⋆〉ℳ, respectively) of a representative sample of 135 nearby (≤ 130 Mpc) LTGs from the CALIFA survey that cover a range between 108.9 M⊙ and 1011.5 M⊙ in total stellar mass ℳ⋆,T. In particular, the analysis here revolves around ⟨δμ9G⟩, a new distance- and formally extinction-independent measure of the contribution by stellar populations of age ≥ 9 Gyr to the mean r-band surface brightness of the bulge. We argue that ⟨δμ9G⟩ offers a handy semi-empirical tracer of the physical and evolutionary properties of LTG bulges and a promising means for their characterization. Results. The essential insight from this study is that LTG bulges form over 3 dex in ℳ⋆ and more than 1 dex in Σ⋆ a tight continuous sequence of increasing ⟨δμ9G⟩ with increasing ℳ⋆, Σ⋆, 〈t⋆〉ℳ and 〈Z⋆〉ℳ. Along this continuum of physical and evolutionary properties, our sample spans a range of ~ 4 mag in ⟨δμ9G⟩: high-⟨δμ9G⟩ bulges are the oldest, densest and most massive ones (〈t⋆〉ℳ ~ 11.7 Gyr, Σ⋆ &gt; 109 M⊙ kpc−2, ℳ⋆ ≥ 1010 M⊙), whereas the opposite is the case for low-⟨δμ9G⟩ bulges (〈t⋆〉ℳ ~ 7 Gyr) that generally reside in low-mass LTGs. Furthermore, we find that the bulge-to-disk age and metallicity contrast, as well as the bulge-to-disk mass ratio, show a positive trend with ℳ⋆,T, raising from, respectively, ~ 0 Gyr, ~ 0 dex and 0.25 to ~ 3 Gyr, ~ 0.3 dex and 0.67 across the mass range covered by our sample. Whereas gas excitation in lower-mass (≲ 109.7 M⊙) bulges is invariably dominated by star formation (SF), LINER- and Seyfert-specific emission-line ratios were exclusively documented in high-mass (≳ 1010 M⊙), high-Σ⋆ (≳ 109 M⊙ kpc−2) bulges. This is in agreement with previous work and consistent with the notion that the Eddington ratio or the black hole-to-bulge mass ratio scale with ℳ⋆. The coexistence of Seyfert and SF activity in ~20% of higher-ℳ⋆, high-Σ⋆ bulges being spectroscopically classified as Composites suggests that the onset of AGN-driven feedback does not necessarily lead to an abrupt termination of SF in LTG nuclei. Conclusions. The continuity both in the properties of LTG bulges themselves and in their age and metallicity contrast to their parent diskssuggests that these components evolve alongside in a concurrent process that leads to a continuum of physical and evolutionary characteristics. Our results are consistent with a picture where bulge growth in LTGs is driven by a superposition of quick-early and slow-secular processes, the relative importance of which increases with ℳ⋆,T. These processes, which presumably combine in situ SF in the bulge and inward migration of material from the disk, are expected to lead to a non-homologous radial growth of Σ⋆ and a trend for an increasing Sérsic index with increasing galaxy mass.

Metasomatic Replacement of Albite in Nature and Experiments

Replacement of albite by sodium-rich, secondary phases is a common phenomenon, observed in different geological settings and commonly attributed to alkaline metasomatism. We investigated growth of nepheline and sodalite on albite in time series experiments between two and 14 days. A total of 42 hydrothermal experiments were performed in cold-seal hydrothermal vessels at a constant pressure of 4 kbar and 200–800 °C in the system SiO2–Al2O3–NaCl–H2O. To allow for fluid flow and material transport, a double-capsule technique was used; hereby, a perforated inner Pt capsule was filled with cleavage fragments of natural albite, whereas the shut outer Au capsule was filled with γ-Al2O3 and the NaCl–H2O solution. Complete overgrowth of albite by sodalite and nepheline occurred after just two days of experiments. At high salinity (≥17 wt % NaCl) sodalite is the stable reaction product over the whole temperature range whereas nepheline occurs at a lower relative bulk salinity than sodalite and is restricted to a high temperature of ≥700 °C. The transformation of albite starts along its grain margins, cracks or twin lamellae. Along the reaction front sodalite crystallizes as small euhedral and highly porous grains forming polycrystalline aggregates. Coarse sodalite dominates in the outermost domains of the reaction zones, suggesting recrystallization. Sodalite may contain fluid inclusions with trapped NaCl-rich brine, demonstrating that the interconnected microporosity provides excellent pathways for fluid-assisted material transport. Highly porous nepheline forms large, euhedral crystals with rectangular outline. Sodalite and nepheline in natural rock samples display only minor porosity but fluid and secondary mineral inclusions, pointing to coarsening of a previously present microporosity. The reaction interface between sodalite and albite in natural rock samples is marked by open channels in transmission electron microscopy. In many of the experiments, a zone of Si–H-rich, amorphous material is developed at the reaction front, which occurs at a temperature of up to of 750 °C as nanometer to 350 µm wide reaction zone around albite. This change in composition corresponds with the abrupt termination of the crystalline feldspar structure. The presence of sodalite as micro- to nanometer-sized, euhedral crystals within the amorphous zone demonstrates, that both the sodalite reaction rim and the amorphous material allow for fluid-assisted material transport between the crystalline albite (release of Si, Al) and the bulk fluid (H2O, Na, Cl). This texture, moreover, suggests that the amorphous phase represents a metastable interstage reaction product, which is progressively replaced by sodalite and nepheline. Remarkably, product sodalite, nepheline, and the amorphous material largely inherit the trace element budget of the respective ancestor albite, indicating that at least part of the trace elements remained fixed during the reaction process. The observed reaction textures in both natural and experimental samples indicate an interfacial dissolution–reprecipitation mechanism. Results of our study bear important implications with respect to mineral replacement in the presence of a fluid phase, especially regarding the interpretation of trace element patterns of the product phases.

Impact of fault evolution in Gilbert-type fan deltas in the Evrostini area, south-central Gulf of Corinth, Greece

Abstract In order to understand how syn-rift deposits are associated with border fault evolution, the outcrops around the Evrostini area in the southern Gulf of Corinth, Greece, are investigated. Two major border fault systems are identified in the study area, which are the Vela–Valimi–Xylokastro and Akrata–Xylokastro border fault complexes. The Vela–Valimi and Xylokastro faults were active in the Calabrian age when the WSW-trending linking faults were initiated at the Evrostini Mountain area and propagated eastwards. The Xylokastro Fault was reactivated in the Middle Pleistocene, when the Akrata Fault was created. It is proposed that WSW-trending faults were developed to link the Akrata and Xylokastro border faults. Longitudinal propagation of the rift margin in the area was segmented by three N–S striking transfer faults. These transfer faults are defined by N–S-aligned discontinuity of abrupt fault displacement termination, large horizontal steps of E–W-striking fault segments, and lateral offsets of syn-rift deposition with major changes in facies. The regional drainages were strongly influenced by border fault growth and along-strike segmentation. Near the tips of the border faults, the drainage may be forced to shift along with fault tip propagation. In contrast, in the boundaries of rift segmentation, the drainage maintains its course and proceeded parallel to the orientation of N–S striking transfer faults. Drainage patterns and their configurations with border fault systems from the field study provide an analog model to predict the sub-surface syn-rift deposits in buried rift basins, such as the North Sea.

(Invited) Digital-Coded Isotope Labeling on Individual Single-Walled Carbon Nanotubes Grown on Crystal Quartz

Single-walled carbon nanotubes (SWNTs) are promising building blocks for next-generation high-performance electronics, e.g. field-effect transistors (FET). For the application, many properties, such as chirality, orientation, density and length, have to be well controlled. Despite significant progresses in controlling the SWNT chirality and density in recent years, further breakthroughs are desirable to make the SWNT-based electronics reality. Detailed understanding on the growth process of individual SWNTs with a practical form (quality, length, and alignment) will accelerate the development of application-oriented growth. In this study, we developed an isotope labeling technique with digital coding for the ex situ monitoring of individual and long (>100 μm) SWNTs. Owing to the nature of ex situ measurement, an enormous number of SWNTs can be characterized on a single substrate. In addition, digital-coding of the isotope labels enables identification of time evolution of SWNT growth with high accuracy. Horizontally aligned configuration were used for the tracing of individual SWNTs and for the breakdown of SWNT quantity into population and length [1]. Aligned SWNTs were grown on r-cut quartz substrates from iron catalysts patterned in stripes with 300-μm separation. Normal 12C ethanol was used for most parts of the growth, but pure 13C ethanol was periodically mixed in various ratios (33, 67, 100 %) to embed digital-coded isotope labels in SWNTs. For the standard growth, 5-sccm ethanol was introduced together with 50-sccm Ar/H2 buffer gas into the reactor with total pressure of ~1.5 kPa. After the growth, position of each isotope label and the SWNT properties were identified by Raman mapping. The sequence of the isotope labels clearly indicated that all the SWNTs that we observed grew in the root growth mode [2], where the catalysts stayed at the original position and SWNTs pushed forward. We obtained the time evolution of SWNT lengths, and found that the SWNTs started to grow after certain lengths of incubation time. For most cases, growth rate was constant until the abrupt termination of the growth. This suggests that the catalytic activity of metal particles did not gradually change with time under the current growth condition. Two different SWNTs with the same chirality (radial breathing mode (RBM) frequency of 190 cm-1 with 532 nm excitation laser) had different growth rates (~8 and ~15 μm/min), indicating the dependence of the growth rate on catalyst sizes or some other properties. For the extraction of intrinsic chirality dependence of the growth rate, we focused on spontaneously formed intramolecular junctions. For example, an intramolecular junction changed the RBM frequencies of an SWNT from 139 to 144 cm-1. Interestingly, the growth rate changed from ~10 to ~8 μm/min along with the chirality change. Since the growth behavior can be traced along individual SWNTs, the dependence on growth conditions, such as temperature and pressure of carbon feedstocks, was also investigated by changing the conditions during the growth. First, ethanol flow rate, which is nearly proportional to the partial pressure, was increased from 3 to 9 sccm in 2 sccm steps every four minutes. Most SWNTs grew faster as the flow rate increased; however, some SWNTs stopped growing for one or two minutes when the flow rate was suddenly increased. We also observed temperature-dependent growth rate, which provides insights into the growth dynamics of individual SWNTs. Part of this work was supported by JSPS KAKENHI Grant Numbers JP25107002, JP15H05760, JP17K06187 and JP17K14601. K.O. was financially supported by a JSPS Fellowship (JP15J07857).

Digital Isotope Coding to Trace the Growth Process of Individual Single-Walled Carbon Nanotubes.

Single-walled carbon nanotubes (SWCNTs) are attracting increasing attention as an ideal material for high-performance electronics through the preparation of arrays of purely semiconducting SWCNTs. Despite significant progress in the controlled synthesis of SWCNTs, their growth mechanism remains unclear due to difficulties in analyzing the time-resolved growth of individual SWCNTs under practical growth conditions. Here we present a method for tracing the diverse growth profiles of individual SWCNTs by embedding digitally coded isotope labels. Raman mapping showed that, after various incubation times, SWCNTs elongated monotonically until their abrupt termination. Ex situ analysis offered an opportunity to capture rare chirality changes along the SWCNTs, which resulted in sudden acceleration/deceleration of the growth rate. Dependence on growth parameters, such as temperature and carbon concentration, was also traced along individual SWCNTs, which could provide clues to chirality control. Systematic growth studies with a variety of catalysts and conditions, which combine the presented method with other characterization techniques, will lead to further understanding and control of chirality, length, and density of SWCNTs.

Basement inheritance and salt structures in the SE Barents Sea: Insights from new potential field data

The tectonic evolution of the former ‘grey zone’ between Russia and Norway has so far remained poorly constrained due to a lack of geophysical data. In 2014, the Geological Survey of Norway (NGU) carried out a new state-of-the-art aeromagnetic survey (BASAR-14) in the southern part of the new Norwegian offshore territory. The new BASAR-14 survey completes and extends the pre-existing aeromagnetic compilation and mapping of the Norwegian Barents Sea. We present this new magnetic dataset and its interpretation combined with gravity and seismic data. Caledonian and Timanian structures, highlighted by the new potential field data, dominate the basement patterns and have exerted a strong influence on the structure and development of the overlying basins and basement highs. Clearly associated with NW-SE-oriented Timanian trends, the Tiddlybanken Basin represents an atypical sag basin that developed at the southern edge of the Fedynsky High. Quantitative modelling along 2D seismic transects was also carried out to constrain the structural and basement composition of the study area. The predominant NE-SW Mesozoic trend of the Nordkapp Basin represents a major crustal hinge zone between the Finnmark Platform, poorly affected by major crustal deformation, and the Bjarmeland Platform where Late Palaeozoic rifting controlled the widespread accumulation of salt deposits in Late Carboniferous-Early Permian time. The entire structure and segmentation of the Nordkapp Basin have been influenced by the inherited basement configuration highlighted by the new aeromagnetic data. At present, quite a few large diapiric salt domes along the Nordkapp and Tiddlybanken basins are relatively shallow, locally reaching the seabed and thus show a clear bathymetric and magnetic signature. Both the Nordkapp and the Tiddlybanken basins appear to lie at the edge of a peculiar thick and rigid crustal feature that coincides with a highly magnetic region. The abrupt termination of the eastern Nordkapp Basin at the edge of this magnetic domain suggests the presence of an old and thick Precambrian continental block. This magnetic and rigid tectonic buffer controlled the Late Palaeozoic pre-salt and Mesozoic post-salt tectonic development of the southeastern Barents Sea.

A hafnium isotopic record of magmatic arcs and continental growth in the Iapetus Ocean: The contrasting evolution of Ganderia and the peri-Laurentian margin

We test the sensitivity of combined U-Pb-Hf isotopic analyses of detrital and magmatic zircon to document complex processes in accretionary orogens, using Ganderia from the Canadian Appalachian orogen as an example. Ganderia hosted a long-lived magmatic arc that began at least by 650Ma and continued until 450Ma, during which time it drifted northward from the Amazonian margin. Its isotopic record suggests arc activity began earlier, possibly at ~750Ma (proto-Ganderia) within an oceanic domain. The U-Pb-Hf zircon isotopic array suggests that Ganderia formed on a sliver of Paleoproterozoic-Mesoproterozoic basement (TDMc=2.2–1.1Ga). A transition towards more evolved Hf isotopic compositions between 650 and 600Ma is interpreted to coincide with its accretion to the Amazonian margin of Gondwana, consistent with other geological evidence. Accretion was followed by increasing amounts of juvenile crustal inputs between ~550 and 500Ma, which is interpreted to reflect subduction roll-back and the onset of drift from the Gondwanan margin. Trench retreat culminated in the separation of the Ganderia arc and formation of the exclusively oceanic ~510–450Ma Penobscot-Popelogan-Victoria arcs on Ganderia. Accretion of Ganderia to the active Notre Dame Subzone along the Laurentian margin occurred in the late Ordovician and is marked by the abrupt termination of Ganderian arc magmatism.The Notre Dame arc evolved along the Laurentian margin between ~515 and 425Ma and was built on Paleoproterozoic-Archean (T(DM)c=2.9–2.5Ga) crust. Supra-subduction zone magmatism occurred at ~490–460Ma during the closure of the Taconic Seaway and was dominated by the recycling of Laurentian crust, with progressive mixing of evolved and juvenile arc magmas over time. The preservation of very evolved Notre Dame arc zircon in Ganderian overstep sequences confirms the arrival of the leading edge of Ganderia to Laurentia by ~450Ma. The hafnium isotopic method is proven here to be a powerful tool when used in conjunction with geological constraints, and is able to identify the changing nature of magmatism during the evolution of complex accretionary systems.

Significant transient pCO2 perturbation at the New Zealand Oligocene-Miocene transition recorded by fossil plant stomata

The reorganisation of Earth's climate system from the Oligocene to the Miocene was influenced by complex interactions between Tethyan tectonics, orbital parameters, oceanographic changes, and carbon cycle feedbacks, with climate modelling indicating that pCO2 was an important factor. Oscillating episodes of climate change during the Oligocene–Miocene transition (OMT) have however been difficult to reconcile with existing pCO2 records. Here we present a new pCO2 record from the OMT into the early Miocene, reconstructed using the stomatal proxy method with a database of fossil Lauraceae leaves from New Zealand. The leaf database derives from three relatively well-dated sites located in the South Island of New Zealand; Foulden Maar, Mataura River and Grey Lake. Atmospheric pCO2 values were obtained based on four separate calibrations with three nearest living equivalents, using the stomatal ratio method as well as transfer functions. Our results, based on the mean values of each of the four calibrations, indicate pCO2 ranging ~582–732 ppm (average 650 ppm) at the OMT, falling precipitously to mean values of ~430–538 ppm (average 492 ppm) for the earliest Miocene and ~454–542 ppm (average 502 ppm) in the early Miocene. The much higher values of pCO2 at the OMT indicate that pCO played an important role in climate dynamics during this time, potentially including the abrupt termination of glaciations.

If started, geoengineering would be hazardous to stop

One way to limit global warming, in addition to reducing emissions of greenhouse gases, is geoengineering—altering the climate through approaches such as injecting sunlight-reflecting sulfur particles into Earth’s stratosphere. Once started, however, an abrupt end to stratospheric aerosol injection (SAI) could be catastrophic for biodiversity, suggests new research led by Christopher H. Trisos of the University of Maryland (Nat. Ecol. Evol. 2018, DOI: 10.1038/s41559-017-0431-0). Trisos and colleagues computationally modeled what would happen if SAI began in 2020 by injecting 5 teragrams of SO2 per year, then maintained at that level until abruptly cutting off in 2070, perhaps because of a change in political will. The researchers observed mixed effects on biodiversity with implementation. Abrupt termination, however, would mean far faster climate change than most species would be able to adapt to. “Thus the adverse impacts of unsustained climate counteraction through SAI are likely to be around three time...

Ichnological and Sedimentological Characteristics of Submarine Fan-Delta Deposits in a Half-Graben, Lower Cretaceous Palnatokes Bjerg Formation, NE Greenland

ABSTRACTFault-scarp related fan deltas developed in tilted half grabens in NE Greenland during late Jurassic—early Cretaceous rifting. This study documents ichnological and sedimentological characteristics of the Lower Cretaceous interval of a submarine fan-delta succession (Palnatokes Bjerg Formation, Wollaston Forland), which represents a time of waning rift activity and transgression. For this purpose, two variably exposed ca. 150 m-thick sections were studied ∼10 km from the coeval fault scarp, near the axis of the most proximal fault block. Moreover, an additional ∼20 m thick coeval succession was studied in the next fault block ∼20 km from the coastline defining fault. The results indicate deposition on the basin floor, in the distal fan and in a mid-fan channel-overbank/splay complex of a subaqueous fan delta. The deposits are characterized mainly by various facies of high and low density turbidity currents, hybrid event beds, and transitional flow facies that grade upward into sediment starved basinal mudstones. The ichnological pattern recorded in these strata is strongly mixed, frequently containing elements of the impoverished Skolithos, Cruziana, Zoophycos ichnofacies, and more rarely of the Nereites ichnofacies. Characteristic features also include suites dominated by infaunal locomotion and feeding trails (including the “Curvolithus suite”) and the common occurrence of crustacean burrows. The results are indicative of a depositional system resembling a fjord-side delta that differs sedimentologically and ichnologically from many other gravity-flow systems of similar grain-size caliber. The ichnological pattern recorded in these strata is potentially a characteristic feature of the subaqueous fan-deltas in comparable settings, reflecting the distinct basin physiography with an abrupt change in bathymetry, a narrow basin geometry, and environmental stress resulting from unstable physical conditions. The counter slope of the rotated fault block may explain the common signs of flow concentration and abrupt fan termination.