Abstract
Magnetic fields (
B
fields) play an important role in molecular cloud fragmentation and star formation but are very difficult to detect. The temporal correlation between the field strength (
...B
) and gas density (
n
) of an isolated cloud has been suggested as an indication of the dynamical importance of
B
fields relative to self-gravity. This temporal
B–n
relation is, however, unobservable. What can be observed using Zeeman measurements are the “spatial
B–n
relations” from the current plane of the sky. Nevertheless, the temporal
B–n
relation argument has still been widely used to interpret observations. Here we present the first numerical test of the legitimacy of this interpretation. From a simulation that can reproduce the observed Zeeman spatial
B
∝
n
2/3
relation, we found that temporal
B
–n
relations of individual cores bear no resemblance to the spatial
B
–n
relations. This result inspired us to discover that the true mechanism behind the 2/3 index is random turbulence compression instead of symmetrical gravitational contraction.
Abstract
The formation of protostellar disks is still a mystery, largely due to the difficulties in observations that can constrain theories. For example, the 3D alignment between the rotation of the ...disk and the magnetic fields (B-fields) in the formation environment is critical in some models, but so far it is impossible to observe. Here we study the possibility of probing the alignment between B-field and disk rotation using “polarization holes” (PHs). PHs are widely observed and are caused by unresolved B-field structures. With ideal magnetohydrodynamic simulations, we demonstrate that different initial alignments between B-field and angular momentum (AM) can result in B-field structures that are distinct enough to produce distinguishable PHs. Thus, PHs can potentially serve as probes for alignments between B-field and AM in disk formation.
The Zeeman effect has been the only method to directly probe the magnetic field strength in molecular clouds. The Bayesian analysis of Zeeman measurements carried out by Crutcher et al. is the only ...reference for cloud magnetic field strength. Here we extended their model and Bayesian analysis of the relation between field strength (B) and volume density (n) in the following three directions based on the recent observational and theoretical development. First, we take R, the observational uncertainty of n, as a parameter to be estimated from data. Second, the restriction of , the index of the B-n relationship, is relieved from 0, 0.75 to 0, 1. Third, we allow f, the minimum-to-maximum B ratio, to vary with n. Our results show that taking R as a parameter provides a better fitting to the B-n relationship and much more reliable estimates on R, f, and the changing point of . Arguably our most important finding is that cannot be reliably estimated by any of the models studied here, either from us or Crutcher et al., if R > 2, which is indeed the case from our estimate. This is the so-called errors-in-variables bias, a well known problem for statisticians.
Graphene, a one‐atom layer of graphite, possesses a unique two‐dimensional structure and excellent mechanical, thermal, and electrical properties. Thus, it has been regarded as an important component ...for making various functional composite materials. Graphene can be prepared through physical, chemical and electrochemical approaches. Among them, chemical methods were tested to be effective for producing chemically converted graphene (CCG) from various precursors (such as graphite, carbon nanotubes, and polymers) in large scale and at low costs. Therefore, CCG is more suitable for synthesizing high‐performance graphene based composites. In this progress report, we review the recent advancements in the studies of the composites of CCG and small molecules, polymers, inorganic nanoparticles or other carbon nanomaterials. The methodology for preparing CCG and its composites has been summarized. The applications of CCG‐based functional composite materials are also discussed.
The recent advancements in the studies of the composites of chemically converted graphene (CCG) and small molecules, polymers, inorganic nanoparticles, or other carbon nanomaterials are reviewed. The methodology for preparing CCG and its composites has been summarized, and the applications of CCG‐based functional composite materials are also discussed.
Esophageal squamous cell carcinoma (ESCC) is one of the deadliest cancers. We performed exome sequencing on 113 tumor-normal pairs, yielding a mean of 82 non-silent mutations per tumor, and 8 cell ...lines. The mutational profile of ESCC closely resembles those of squamous cell carcinomas of other tissues but differs from that of esophageal adenocarcinoma. Genes involved in cell cycle and apoptosis regulation were mutated in 99% of cases by somatic alterations of TP53 (93%), CCND1 (33%), CDKN2A (20%), NFE2L2 (10%) and RB1 (9%). Histone modifier genes were frequently mutated, including KMT2D (also called MLL2; 19%), KMT2C (MLL3; 6%), KDM6A (7%), EP300 (10%) and CREBBP (6%). EP300 mutations were associated with poor survival. The Hippo and Notch pathways were dysregulated by mutations in FAT1, FAT2, FAT3 or FAT4 (27%) or AJUBA (JUB; 7%) and NOTCH1, NOTCH2 or NOTCH3 (22%) or FBXW7 (5%), respectively. These results define the mutational landscape of ESCC and highlight mutations in epigenetic modulators with prognostic and potentially therapeutic implications.
Abstract
Molybdenum nitride (δ–MoN) is an important functional material due to its impressive catalytic, energy storage, and superconducting properties. However, the synthesis of δ–MoN usually ...requires extremely harsh conditions; thus, the insight into δ−MoN is far behind that of oxides and sulfides of molybdenum. Herein, we report that ultrathin δ−MoN nanosheets are prepared at 270 °C and 12 atm. WN, VN, and TiN nanosheets are also synthesized by this method. The δ−MoN nanosheets show strong surface plasmon resonance, high conductivity, excellent thermal and chemical stability as well as a high photothermal conversion efficiency of 61.1%. As a promising surface enhanced Raman scattering substrate, the δ−MoN nanosheets exhibit a 8.16 × 10
6
enhanced factor and a 10
−10
level detection limit for polychlorophenol.
The orientations of filamentary molecular clouds in the Gould Belt and their local intercloud media (ICM) magnetic fields are studied using near-infrared dust extinction maps and optical stellar ...polarimetry data. These filamentary clouds are a few-to-10 pc in length, and we find that their orientations tend to be either parallel or perpendicular to the mean field directions of the local ICM. This bimodal distribution is not found in cloud simulations with super-Alfvenic turbulence, in which the cloud orientations should be random. ICM magnetic fields that are dynamically important compared to inertial range turbulence and self-gravity can readily explain both field-filament configurations. Previous studies commonly recognize that strong magnetic fields can guide gravitational contraction and result in filaments perpendicular to them, but few discuss the fact that magnetic fields can also channel sub-Alfvenic turbulence to form filaments aligned with them. This strong-field scenario of cloud formation is also consistent with the constant field strength observed from ICM to clouds and is possible to explain the "hub-filament" cloud structure and the density threshold of cloud gravitational contraction. PUBLICATION ABSTRACT
Abstract
The view on velocity structures in molecular clouds and their relationship with magnetic fields (
B
field) has evolved during the past decade from almost no correlation to highly parallel. ...Our numerical simulations suggest a more nuanced picture: Depending on whether the self-gravity is dynamically dominant, the velocity field can be governed by either contraction (at high densities) or turbulence (at low densities), and their anisotropies will tend to be either perpendicular or parallel, respectively, to the
B
fields. High-density regions are always embedded in the low-density fore/background, so the velocity behaviors from lines of sight (LOSs) with high column densities will be a mixture of orthogonal anisotropies, which can be hard to interpret and necessitates zooming in onto certain LOS scales to better characterize localized behaviors. We tested and confirmed the above prediction with CO observations of the Taurus molecular cloud.
A breath figure (BF) is the water droplet array that forms when moisture comes in contact with a cold substrate. This water droplet array has been widely utilized in the past two decades as a ...versatile soft template for the fabrication of polymeric porous films. Accordingly, the ordered pores on the polymer films formed with such a method are named a breath figure array (BFA).The BF templating technique is undergoing rapid development. Several unconventional BF processes have been established to prepare porous films with unique morphologies or primary materials, and various newly developed functionalization techniques have significantly improved the performance of polymeric films with BFA, leading to novel applications, including templates, biosensors, and separation membranes. These recent achievements will be described in this Minireview.
Every breath you take: A breath figure (BF) is the water droplet array that forms when moisture comes in contact with a cold substrate. Several unconventional BF methods have been established to prepare BF array films with unique morphologies or primary materials, and various newly developed functionalization techniques have significantly improved the performance of BF array films, leading to some novel applications.
Conducting polymers (CPs) have been extensively studied and widely applied in various organic devices. To improve the performances or extend the functions of the devices, CPs usually have to be ...nanostructured. Electrosynthesis provides an effective and convenient one-step approach to CP nanomaterials. The resulting materials are usually oriented on the electrode surfaces and their properties are easy to be controlled. This critical review focuses on the syntheses of CP nanostructures and nanocomposites by electrochemical polymerization. The applications of the nanomaterials in organic devices such as sensors, actuators and memory devices also will be discussed (111 references).
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