Abstract
Scattered-light imaging studies have detected nearly two dozen spiral arm systems in circumstellar disks, yet the formation mechanisms for most of them are still under debate. Although ...existing studies can use motion measurements to distinguish leading mechanisms such as planet–disk interaction and disk self-gravity, close-in stellar flybys can induce short-lived spirals and even excite arm-driving planets into highly eccentric orbits. With unprecedented stellar location and proper-motion measurements from Gaia Data Release 3 (DR3), here we study for known spiral arm systems their flyby history with their stellar neighbors by formulating an analytical on-sky flyby framework. For stellar neighbors currently located within 10 pc of the spiral hosts, we restrict the flyby time to within the past 10
4
yr and the flyby distance to within 10 times the disk extent in scattered light. Among a total of 12,570 neighbors that are identified in Gaia DR3 for 20 spiral systems, we do not identify credible flyby candidates for isolated systems. Our analysis suggests that a close-in recent flyby is not the dominant formation mechanism for isolated spiral systems in scattered light.
Proteins perform vital functional and structural duties in living systems, and the in-depth investigation of protein in its native state is one of the most important challenges in the postgenomic ...era. Surface-enhanced Raman spectroscopy (SERS) can provide the intrinsic fingerprint information of samples with ultrahigh sensitivity but suffers from the reproducibility and reliability issues. In this paper, we proposed an iodide-modified Ag nanoparticles method (Ag IMNPs) for label-free detection of proteins. The silver nanoparticles provide the huge enhancement to boost the Raman signal of proteins, and the coated iodide layer offers a barrier to prevent the direct interaction between the proteins and the metal surface, helping to keep the native structures of proteins. With this method, highly reproducible and high-quality SERS signals of five typical proteins (lysozyme, avidin, bovine serum albumin, cytochrome c, and hemoglobin) have been obtained, and the SERS features of the proteins without chromophore were almost identical to the respective normal Raman spectra. This unique feature allows the qualitative identification of them by simply taking the intensity ratio of the Raman peaks of tryptophan to phenylalanine residues. We further demonstrated that the method can also be used for label-free multiplex analysis of protein mixture as well as to study the dynamic process of protein damage stimulated by hydrogen peroxide. This method proves to be very promising for further applications in proteomics and biomedical research.
Abstract
Observations and theories reveal that star-forming regions eject their members during the early evolution of the cluster. We present an initial search for stars ejected from the young ...cluster IC 348 based on an analysis of Gaia EDR3 astrometry of previously identified members. We identify six candidate walkaway stars with projected velocities of 5–8 km s
−1
. The candidate with properties most consistent with a walkaway star, V701 Per, was likely ejected from a small group to the west of IC 348. Three candidates are currently located or have proper motions that trace back to the center of IC 348, though their classification as walkaway stars may also be affected by large astrometric errors. Two other candidate walkaway stars were likely born in other subgroups around IC 348 within the Perseus star-forming region. Since our search criteria are restricted to previously identified members of IC 348, we did not identify any stars that were ejected at high velocities and traveled far from the cluster. Our study suggests that ejections have potentially occurred in both the central region of IC 348 and other subgroups in Perseus. Extending the search range will lead to more candidate ejections and constrain the dynamic properties and evolution of IC 348 by comparing with simulations.
Polarization modulation and multichannel beam generation are crucial in multichannel communication and high-resolution imaging at THz frequency. In this work, we present a polarization-reprogrammable ...coding metasurface composed of VO 2 /Au composite concentric rings (CCRs). Owing to the phase-change property of VO 2 , the CCR is designed as a digital coding element for the polarization conversion. When VO 2 remains insulator state at room temperature, the y -polarized incident wave is transformed into x -polarized wave, which can be regarded as digital state 0. When VO 2 converts into metal state at critical temperature (68 °C), the polarization of reflected wave stays unchanged, corresponding to digital state 1. Any desired linear polarization state of reflected beam is achieved by taking advantage of different coding sequences in a programmable manner. Furthermore, by combining phase gradient with polarization coding states, we propose an anisotropic programmable metasurface to control the multi-channel reflected beams dynamically. By arranging distinct coding sequences, we show that the EM reflected beams can be manipulated flexibly. The proposed programmable metasurface paves new ways towards THz polarization manipulation, signal detection and information communication.
After over 30 years of development, surface-enhanced Raman spectroscopy (SERS) is now facing a very important stage in its history. The explosive development of nanoscience and nanotechnology has ...assisted the rapid development of SERS, especially during the last 5 years. Further development of surface-enhanced Raman spectroscopy is mainly limited by the reproducible preparation of clean and highly surface enhanced Raman scattering (SERS) active substrates. This review deals with some substrate-related issues. Various methods will be introduced for preparing SERS substrates of Ag and Au for analytical purposes, from SERS substrates prepared by electrochemical or vacuum methods, to well-dispersed Au or Ag nanoparticle sols, to nanoparticle thin film substrates, and finally to ordered nanostructured substrates. Emphasis is placed on the analysis of the advantages and weaknesses of different methods in preparing SERS substrates. Closely related to the application of SERS in the analysis of trace sample and unknown systems, the existing cleaning methods for SERS substrates are analyzed and a combined chemical adsorption and electrochemical oxidation method is proposed to eliminate the interference of contaminants. A defocusing method is proposed to deal with the laser-induced sample decomposition problem frequently met in SERS measurement to obtain strong signals. The existing methods to estimate the surface enhancement factor, a criterion to characterize the SERS activity of a substrate, are analyzed and some guidelines are proposed to obtain the correct enhancement factor.
To address the uncontrollable risks associated with the overreliance on ship operators' driving in current ship safety braking methods, this study aims to reduce the impact of operator fatigue on ...navigation safety. Firstly, this study established a human-ship-environment monitoring system with functional and technical architecture, emphasizing the investigation of a ship braking model that integrates brain fatigue monitoring using electroencephalography (EEG) to reduce braking safety risks during navigation. Subsequently, the Stroop task experiment was employed to induce fatigue responses in drivers. By utilizing principal component analysis (PCA) to reduce dimensionality across multiple channels of the data acquisition device, this study extracted centroid frequency (CF) and power spectral entropy (PSE) features from channels 7 and 10. Additionally, a correlation analysis was conducted between these features and the Fatigue Severity Scale (FSS), a five-point scale for assessing fatigue severity in the subjects. This study established a model for scoring driver fatigue levels by selecting the three features with the highest correlation and utilizing ridge regression. The human-ship-environment monitoring system and fatigue prediction model proposed in this study, combined with the ship braking model, achieve a safer and more controllable ship braking process. By real-time monitoring and prediction of driver fatigue, appropriate measures can be taken in a timely manner to ensure navigation safety and driver health.
Abstract
Complex assembly tasks with multiple manual operations and steps often require rapid judgment and action under time pressure and cause most human-related errors. The task switching and ...action transitions are major sources of these errors. This study intends to implement an electroencephalography (EEG) approach to quantitatively evaluate the mental workload during task switching and transition. The time–frequency and spectrum analysis were utilized to compute and reflect the task demand between the intervals of individual tasks. This study developed an experiment to validate the proposed assessment approach and benchmark the results with the National Aeronautics and Space Administration task load index (NASA-TLX) subjective evaluation scale analysis. The results show that the average value of the power spectral densities (PSDs) of the gamma band signal of the AF4 channel and the beta band signal of Channel F3 show distinctive signal patterns among task stages and intervals. During the interval between the idling stage and the part selection stage, the peak of the PSD envelope increased from 18 to 27 Hz, suggesting advanced cognition increases the mental workload of the interval between different tasks. Therefore, the task switching period cannot be regarded as rest and need to be optimized with better task organization.
CRISPR technologies enabling precise genome manipulation are valuable for gene function studies and molecular crop breeding. However, the requirement of a protospacer adjacent motif (PAM), such as ...NGG and TTN, for Cas protein recognition restricts the selection of targetable genomic loci in practical applications of CRISPR technologies. Recently Cas9-NG, which recognizes a minimal NG PAM, was reported to expand the targeting space of genome editing in human cells, but it remains unclear whether this Cas9 variant can be used in plants. In this study, we evaluated the nuclease activity of Cas9-NG toward various NGN PAMs by targeting endogenous genes in transgenic rice. We found that Cas9-NG edits all NGG, NGA, NGT, and NGC sites with impaired activity, while the gene-edited plants were dominated by monoallelic mutations. Cas9-NG-engineered base editors were then developed and used to generate OsBZR1 gain-of-function plants that can not be created by other available Cas9-engineered base editors. Moreover, we showed that a Cas9-NG-based transcriptional activator efficiently upregulated the expression of endogenous target genes in rice. In addition, we discovered that Cas9-NG recognizes NAC, NTG, NTT, and NCG apart from NG PAM. Together, these findings demonstrate that Cas9-NG can greatly expand the targeting scope of genome-editing tools, showing great potential for targeted genome editing, base editing, and genome regulation in plants.
Cas9-NG endonuclease recognizes NG, NAC, NTG, NTT and NCG PAM, inducing target gene mutations in rice. Cas9-NG nickase is compatible with nucleoside deaminases and transcriptional activation domain, functioning in base editing and transcriptional regulation of target gene in rice.
To characterize circumstellar systems in high-contrast imaging, the fundamental step is to construct a best point-spread function (PSF) template for the noncircumstellar signals (i.e., starlight and ...speckles) and separate it from the observation. With existing PSF construction methods, the circumstellar signals (e.g., planets, circumstellar disks) are unavoidably altered by overfitting and/or self-subtraction, making forward modeling a necessity to recover these signals. We present a forward modeling-free solution to these problems with data imputation using sequential nonnegative matrix factorization (DI-sNMF), which first converts this signal separation problem to a "missing data" problem in statistics by flagging the regions that host circumstellar signals as missing data, then attributes PSF signals to these regions. We mathematically prove it to have negligible alteration to circumstellar signals when the imputation region is relatively small, which thus enables precise measurement of these circumstellar objects. We apply it to simulated point-source and circumstellar disk observations to demonstrate its proper recovery of them. We apply it to Gemini Planet Imager K1-band observations of the debris disk surrounding HR 4796A, finding a tentative trend that the dust is more forward scattering as the wavelength increases. We expect DI-sNMF to be applicable to other general scenarios where the separation of signals is needed.
Abstract We present JWST Early Release Science coronagraphic observations of the super-Jupiter exoplanet, HIP 65426b, with the Near-Infrared Camera (NIRCam) from 2 to 5 μ m, and with the Mid-Infrared ...Instrument (MIRI) from 11 to 16 μ m. At a separation of ∼0.″82 (87 − 31 + 108 au), HIP 65426b is clearly detected in all seven of our observational filters, representing the first images of an exoplanet to be obtained by JWST, and the first-ever direct detection of an exoplanet beyond 5 μ m. These observations demonstrate that JWST is exceeding its nominal predicted performance by up to a factor of 10, depending on separation and subtraction method, with measured 5 σ contrast limits of ∼1 × 10 −5 and ∼2 × 10 −4 at 1″ for NIRCam at 4.4 μ m and MIRI at 11.3 μ m, respectively. These contrast limits provide sensitivity to sub-Jupiter companions with masses as low as 0.3 M Jup beyond separations of ∼100 au. Together with existing ground-based near-infrared data, the JWST photometry are fit well by a BT-SETTL atmospheric model from 1 to 16 μ m, and they span ∼97% of HIP 65426b's luminous range. Independent of the choice of model atmosphere, we measure an empirical bolometric luminosity that is tightly constrained between log L bol / L ⊙ = −4.31 and −4.14, which in turn provides a robust mass constraint of 7.1 ± 1.2 M Jup . In totality, these observations confirm that JWST presents a powerful and exciting opportunity to characterize the population of exoplanets amenable to high-contrast imaging in greater detail.
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