Discovering and optimizing commercially viable materials for clean energy applications typically takes more than a decade. Self-driving laboratories that iteratively design, execute, and learn from ...materials science experiments in a fully autonomous loop present an opportunity to accelerate this research process. We report here a modular robotic platform driven by a model-based optimization algorithm capable of autonomously optimizing the optical and electronic properties of thin-film materials by modifying the film composition and processing conditions. We demonstrate the power of this platform by using it to maximize the hole mobility of organic hole transport materials commonly used in perovskite solar cells and consumer electronics. This demonstration highlights the possibilities of using autonomous laboratories to discover organic and inorganic materials relevant to materials sciences and clean energy technologies.
Summary
The potential interaction between chronic hepatitis B (CHB) and nonalcoholic fatty liver disease (NAFLD), two of the most prevalent liver diseases worldwide, has not been well defined. We ...performed liver stiffness (LS) and controlled attenuation parameter (CAP) measurements using transient elastography in 1202 CHB patients. Of these, 601 steatotic patients were matched with nonsteatotic controls in a 1:1 ratio by age, gender, nucleoside analogue treatment status, and treatment duration. Severe fibrosis was defined according to EASL‐ALEH criteria, and steatosis was defined as CAP ≥222 dB m−1. Anthropometric measurements and metabolic‐related parameters were recorded. The mean age of the 1202 patients (51.4% male) was 51.8 years. 696 patients (57.9%) were on nucleoside analogues for a median duration of 76.2 months. Among treatment‐naïve patients, median serum HBV DNA was lower in steatotic individuals than in controls (3.0 vs 3.4 log IU mL−1, P < .05), with this inverse relationship remaining significant in multivariate analysis (odds ratio 0.859, 95% CI 0.743‐0.994, P < .05). With increased steatosis severity, there was a stepwise decrease in median HBV DNA levels (3.1 and 2.6 log IU mL−1 in no steatosis and severe steatosis, respectively, P = .032). Steatosis was associated with a higher median LS (5.4 kPa vs 5.0 kPa, P < .001). Severe steatosis, when compared to mild/moderate steatosis, was associated with an increased percentage of severe fibrosis (23.2% and 12.6%, respectively, P = .005). We conclude that severe steatosis was associated with increased fibrosis in CHB patients. Increasing steatosis was independently associated with lower serum HBV DNA levels, suggesting its potential negative effects on viral replication.
Previous studies have evaluated how changes in atmospheric nitrogen (N) inputs and climate affect stream N concentrations and fluxes, but none have synthesized data from sites around the globe. We ...identified variables controlling stream inorganic N concentrations and fluxes, and how they have changed, by synthesizing 20 time series ranging from 5 to 51 years of data collected from forest and grassland dominated watersheds across Europe, North America, and East Asia and across four climate types (tropical, temperate, Mediterranean, and boreal) using the International Long-Term Ecological Research Network. We hypothesized that sites with greater atmospheric N deposition have greater stream N export rates, but that climate has taken a stronger role as atmospheric deposition declines in many regions of the globe. We found declining trends in bulk ammonium and nitrate deposition, especially in the longest time-series, with ammonium contributing relatively more to atmospheric N deposition over time. Among sites, there were statistically significant positive relationships between (1) annual rates of precipitation and stream ammonium and nitrate fluxes and (2) annual rates of atmospheric N inputs and stream nitrate concentrations and fluxes. There were no significant relationships between air temperature and stream N export. Our long-term data shows that although N deposition is declining over time, atmospheric N inputs and precipitation remain important predictors for inorganic N exported from forested and grassland watersheds. Overall, we also demonstrate that long-term monitoring provides understanding of ecosystems and biogeochemical cycling that would not be possible with short-term studies alone.
As an important species of the Martian thermosphere, NO is chemically and radiatively active. However, its abundance is poorly constrained due to difficulties in both remote sensing and in situ ...measurements. In this study, we use the Neutral Gas and Ion Mass Spectrometer measurements made onboard the Mars Atmosphere and Volatile Evolution to derive the N(4S), N(2D), and NO abundances in the Martian thermosphere based on time‐dependent odd N chemistry. At a reference altitude of 160 km, our calculations suggest that the NO abundance is maximized in the afternoon whereas the N(4S) and N(2D) abundances maximized in the morning, both driven by the variation of the ambient N2 mixing ratio. The difference in chemical loss time scale implies a strong diurnal variation for NO and N(2D) but a weak variation for N(4S).
Plain language summary
NO is usually regarded as a good tracer of energy input into the upper atmospheres of terrestrial planets. On Mars, NO is mainly produced via the reaction of atomic N in the excited state with ambient CO2 and lost via the reaction with atomic N in the ground state. Existing investigations of NO abundance in the Martian upper atmosphere are extremely limited due to difficulties in both remote sensing and in situ measurements. In this study, we propose a useful approach to determine the NO abundance on both the dayside and nightside of Mars by combining our knowledge of the odd N chemistry with available neutral and ion density measurements of relevant chemical reactants. On the dayside, we find the NO abundance to be maximized late in the afternoon, which is driven by the variation of N2 mixing ratio in the background atmosphere. Our analysis also allows the diurnal variation of NO to be explored for the first time, revealing a strong day‐night difference by 3 orders of magnitude. This is caused by the fast depletion of NO on the nightside where its production source drops to a minimum level in the absence of solar radiation.
Key Points
The odd N abundances at 160 km in the Martian thermosphere are calculated with time‐dependent chemistry
The NO abundance is maximized in the afternoon whereas the N(4S) and N(2D) abundances maximized in the morning
A strong diurnal variation is present for NO and N(2D) but a weak diurnal variation present for N(4S)
NASA’s InSight mission to Mars will measure seismic signals to determine the planet’s interior structure. These highly sensitive seismometers are susceptible to corruption of their measurements by ...environmental changes. Magnetic fields, atmosphere pressure changes, and local winds can all induce apparent changes in the seismic records that are not due to propagating ground motions. Thus, InSight carries a set of sensors called the Auxiliary Payload Sensor Suite (APSS) which includes a magnetometer, an atmospheric pressure sensor, and a pair of wind and air temperature sensors. In the case of the magnetometer, knowledge of the amplitude of the fluctuating magnetic field at the InSight lander will allow the separation of seismic signals from potentially interfering magnetic signals of either natural or spacecraft origin. To acquire such data, a triaxial fluxgate magnetometer was installed on the deck of the lander to obtain magnetic records at the same cadence as the seismometer. Similarly, a highly sensitive pressure sensor is carried by InSight to enable the removal of local ground-surface tilts due to advecting pressure perturbations. Finally, the local winds (speed and direction) and air temperature are estimated using a hot-film wind sensor with heritage from REMS on the Curiosity rover. When winds are too high, seismic signals can be ignored or discounted. Herein we describe the APSS sensor suite, the test programs for its components, and the possible additional science investigations it enables.
Since loss of function mutations of PINK1 lead to early onset Parkinson’s disease, there has been growing interest in the discovery of small molecules that amplify the kinase activity of PINK1. We ...herein report the design, synthesis, serum stability, and hydrolysis of four kinetin riboside ProTides. These ProTides, along with kinetin riboside, activated PINK1 in cells independent of mitochondrial depolarization. This highlights the potential of modified nucleosides and their phosphate prodrugs as treatments for neurodegenerative diseases.
Inositol polyphosphate 4-phosphatase type II (INPP4B) negatively regulates phosphatidylinositol 3-kinase signaling and is a tumor suppressor in some types of cancers. However, we have found that it ...is frequently upregulated in human colon cancer cells. Here we show that silencing of INPP4B blocks activation of Akt and serum- and glucocorticoid-regulated kinase 3 (SGK3), inhibits colon cancer cell proliferation and retards colon cancer xenograft growth. Conversely, overexpression of INPP4B increases proliferation and triggers anchorage-independent growth of normal colon epithelial cells. Moreover, we demonstrate that the effect of INPP4B on Akt and SGK3 is associated with inactivation of phosphate and tensin homolog through its protein phosphatase activity and that the increase in INPP4B is due to Ets-1-mediated transcriptional upregulation in colon cancer cells. Collectively, these results suggest that INPP4B may function as an oncogenic driver in colon cancer, with potential implications for targeting INPP4B as a novel approach to treat this disease.
Flux transfer events observed at Mercury, Earth, and Jupiter are attributed to spatially and temporally limited events in which the magnetosheath and magnetospheric magnetic field become ...interconnected and magnetic flux is transported from the dayside to the lobes of the magnetotail. Examination of the Saturnian magnetopause at local times from 1000 to 1400 shows no evidence for this phenomenon. Nevertheless, we do find brief intervals during which the normal component of the magnetic field across the magnetopause becomes significantly enhanced for typically one to ten minutes. Magnetosheath electrons appear during these episodes of enhanced magnetic field normal components indicating that indeed the magnetosphere is connected to the magnetosheath by these magnetic bridges. To determine if this magnetic connection leads to a measurable transfer of magnetic flux from the dayside, we check the location of the magnetopause standoff distance for both northward and southward magnetosheath fields. In 71 crossings, we find no obvious dependence of the distance on the direction of the magnetosheath field, indicating that the direction of the interplanetary magnetic field is not a major factor in the determination of the location of the Saturnian magnetopause. This is unlike the position of the terrestrial magnetosphere that undergoes significant motion through reconnection with the interplanetary magnetic field.
Key Points
Flux transfer events are not seen at the Saturn magnetopause
Magnetopause location not correlated with magnetosheath magnetic field
Connected flux tubes are found across magnetopause
Despite produced exclusively on the dayside, photoelectrons, as an important population of the Martian ionosphere, have also been observed on the nightside. Here we present a statistical survey of ...nightside photoelectrons using the suprathermal electron measurements, made by the Solar Wind Electron Analyzer onboard the Mars Atmosphere and Volatile Evolution. We find that nearly 30% of the available nightside suprathermal electron spectra show clear photoelectron signatures. Nightside photoelectrons have an occurrence rate that decreases with increasing solar zenith angle and they are characterized by a preferentially field‐aligned pitch angle distribution. Our analysis also suggests that nightside photoelectrons are less likely observed under the high solar wind condition. These observations are favorably interpreted by the scenario of photoelectron transport along cross‐terminator magnetic field lines, as supported by a simplified test particle model. Our study highlights a complex plasma environment near Mars modulated by both internal and external conditions.
Plain Language Summary
Photoelectrons are an important population of a planetary upper atmosphere that plays a crucial role in ionization, heating, radiation, and escape. Despite that photoelectrons are ideally produced by solar radiation on the dayside only, they have also been observed on the nightside of a planet such as Mars. This study is devoted to a statistical survey of photoelectrons in the nightside Martian upper atmosphere, based on the state‐of‐the‐art measurements made by the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. A surprisingly large fraction of photoelectron energy spectra is identified on the nightside of Mars, occupying nearly 30% of the available nightside measurements. Meanwhile, substantial variations in the observations of nightside photoelectrons are suggested by the data, revealing that (1) their occurrence rate declines rapidly near and beyond the terminator; (2) their velocities are more likely parallel to the ambient magnetic field lines; and (3) they are less likely observed under high solar wind dynamic pressures. These observations could be interpreted by photoelectron transport along large‐scale magnetic field lines from their dayside source regions to the nightside, a scenario that is controlled by both internal and external conditions and thus provides a useful diagnostic of the ambient magnetic field configuration.
Key Points
The photoelectron occurrence rate in the nightside Martian ionosphere decreases with increasing solar zenith angle
Nightside photoelectrons are observed to be preferentially field‐aligned, as a natural result of cross‐terminator transport
Nightside photoelectrons are more likely observed under low solar wind dynamical pressures
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