Synthesis of unlayered graphene from carbon droplets: In stars and in the lab

Mikrometergroße präsolare Teilchen von dem Meteorit Murchison bildeten sich, so kann es aus der isotopischen Zusammensetzung gefolgert werden, in der Umgebung von AGB (asymptotischen Riesenast)-Sternen aus kurz zuvor entstandenen Kohlenstoffatomen. Zu diesen präsolaren Teilchen zählen graphitberandete Teilchen mit und ohne kugelförmigem Kern aus {\em einander kreuzenden} Graphenschichten. Der Ursprung dieses ungeschichteten Materials, das eine Dichte ähnlich der von Graphit besitzt, war ein Rätsel, da sp2-Kohlenstoff häufig selbst dann eine Schichtung (die beispielsweise mittels Elektronenbeugung beobachteten 0.34-Nanometer-Abstände) aufweist, wenn er nahezu amorph ist. Wir zeigen auf, dass derartige Teilchen, bestehend aus Kern und Umhüllung, im Labor in einem "Kohlenstoffverdunstungsofen" hergestellt werden können. Dort kondensieren die Kerne vermutlich als unterkühlte Tropfen flüssigen Kohlenstoffs, der langsam genug fest wird, dass die Graphenschichten mit gegenseitigen Kreuzungen wachsen können. Schichtkohärenzbreiten von 1 bis 2 (verglichen mit 4) Nanometern in unseren ersten "selbsterzeugten" Kernen sprechen für im Vergleich zum präsolaren Fall kürzere Erstarrungszeiten. Die Beobachtungen ebnen der Weg, astrophysikalische Dampfkondensation zu simulieren und damit weitere Laborexperimente zu ermöglichen. Die Temperaturen und Drücke, die nötig sind, um unterkühlte flüssige Tropfen wachsen zu lassen, legen nahe, dass sich die Teilchen, bestehend aus Kern und Umhüllung, während des dritten "dredge-up" im innersten Teil der Photosphäre bildeten, nicht in äußeren Sternenwinden. Dieses präsolare Material hat möglicherweise bereits beispiellose diffusionshindernde Eigenschaften. Allerdings bleibt die Synthese von Schichten mit höherer Kohärenzbreite im Labor eine Herausforderung.Micron-sized presolar particles from meteorite Murchison show isotopic evidence of formation from freshly made carbon atoms, around asymptotic giant branch stars. These include graphite-rimmed particles with and without a spherical core of apparently intergrown graphene. The origin of this unlayered material (with a density near that of graphite) was a puzzle, since sp2 carbon often shows layering (e.g. 0.34 nanometer spacing in electron diffraction or images) even when nearly amorphous. We show that such core-rim particles can be grown in a laboratory evaporating carbon oven, where the cores likely condense as supercooled droplets of carbon liquid that solidify slowly enough for intergrowth of graphene sheets. Sheet coherence widths from 1 to 2 (compared to 4) nanometers in our first homemade cores suggest solidification times shorter than for the presolar case. The observations point the way to simulating astrophysical carbon vapor condensation, setting the stage for more laboratory experiments. The temperatures and pressures needed to grow supercooled liquid droplets suggest that the core-rim particles formed in third dredge-up eruptions at the photosphere base, rather than in external stellar winds. This presolar material may already have unprecedented properties in blocking diffusion, although synthesizing increased coherence-width sheets in the lab remains a challenge

Obstacles, Interfacial Forms, and Turbulence: A Numerical Analysis of Soil–Water Evaporation Across Different Interfaces

AbstractExchange processes between a turbulent free flow and a porous media flow are sensitive to the flow dynamics in both flow regimes, as well as to the interface that separates them. Resolving these complex exchange processes across irregular interfaces is key in understanding many natural and engineered systems. With soil–water evaporation as the natural application of interest, the coupled behavior and exchange between flow regimes are investigated numerically, considering a turbulent free flow as well as interfacial forms and obstacles. Interfacial forms and obstacles will alter the flow conditions at the interface, creating flow structures that either enhance or reduce exchange rates based on their velocity conditions and their mixing with the main flow. To evaluate how these interfacial forms change the exchange rates, interfacial conditions are isolated and investigated numerically. First, different flow speeds are compared for a flat surface. Second, a porous obstacle of varied height is introduced at the interface, and the effects the flow structures that develop have on the interface are analyzed. The flow parameters of this obstacle are then varied and the interfacial exchange rates investigated. Next, to evaluate the interaction of flow structures between obstacles, a second obstacle is introduced, separated by a varied distance. Finally, the shape of these obstacles is modified to create different wave forms. Each of these interfacial forms and obstacles is shown to create different flow structures adjacent to the surface which alter the mass, momentum, and energy conditions at the interface. These changes will enhance the exchange rate in locations where higher velocity gradients and more mixing with the main flow develop, but will reduce the exchange rate in locations where low velocity gradients and limited mixing with the main flow occur

Tour the United VCU, The Premier Urban Research University

This project will capitalize on the existing Open House weekends by offering a 60 minute tour of the MCV Campus. The tour will expose prospective students to VCU as a whole, highlighting the diverse range of studies and to present VCU as one university. The bus ride and walking tour will showcase the connection and relevance of both campuses, allowing prospective students with a myriad of interests to see all that VCU has to offer

Pan-Cancer Analysis of lncRNA Regulation Supports Their Targeting of Cancer Genes in Each Tumor Context

Long noncoding RNAs (lncRNAs) are commonly dys-regulated in tumors, but only a handful are known toplay pathophysiological roles in cancer. We inferredlncRNAs that dysregulate cancer pathways, onco-genes, and tumor suppressors (cancer genes) bymodeling their effects on the activity of transcriptionfactors, RNA-binding proteins, and microRNAs in5,185 TCGA tumors and 1,019 ENCODE assays.Our predictions included hundreds of candidateonco- and tumor-suppressor lncRNAs (cancerlncRNAs) whose somatic alterations account for thedysregulation of dozens of cancer genes and path-ways in each of 14 tumor contexts. To demonstrateproof of concept, we showed that perturbations tar-geting OIP5-AS1 (an inferred tumor suppressor) andTUG1 and WT1-AS (inferred onco-lncRNAs) dysre-gulated cancer genes and altered proliferation ofbreast and gynecologic cancer cells. Our analysis in-dicates that, although most lncRNAs are dysregu-lated in a tumor-specific manner, some, includingOIP5-AS1, TUG1, NEAT1, MEG3, and TSIX, synergis-tically dysregulate cancer pathways in multiple tumorcontexts

Pan-cancer Alterations of the MYC Oncogene and Its Proximal Network across the Cancer Genome Atlas

Although theMYConcogene has been implicated incancer, a systematic assessment of alterations ofMYC, related transcription factors, and co-regulatoryproteins, forming the proximal MYC network (PMN),across human cancers is lacking. Using computa-tional approaches, we define genomic and proteo-mic features associated with MYC and the PMNacross the 33 cancers of The Cancer Genome Atlas.Pan-cancer, 28% of all samples had at least one ofthe MYC paralogs amplified. In contrast, the MYCantagonists MGA and MNT were the most frequentlymutated or deleted members, proposing a roleas tumor suppressors.MYCalterations were mutu-ally exclusive withPIK3CA,PTEN,APC,orBRAFalterations, suggesting that MYC is a distinct onco-genic driver. Expression analysis revealed MYC-associated pathways in tumor subtypes, such asimmune response and growth factor signaling; chro-matin, translation, and DNA replication/repair wereconserved pan-cancer. This analysis reveals insightsinto MYC biology and is a reference for biomarkersand therapeutics for cancers with alterations ofMYC or the PMN

Genomic, Pathway Network, and Immunologic Features Distinguishing Squamous Carcinomas

This integrated, multiplatform PanCancer Atlas study co-mapped and identified distinguishing molecular features of squamous cell carcinomas (SCCs) from five sites associated with smokin

Spatial Organization and Molecular Correlation of Tumor-Infiltrating Lymphocytes Using Deep Learning on Pathology Images

Beyond sample curation and basic pathologic characterization, the digitized H&E-stained images of TCGA samples remain underutilized. To highlight this resource, we present mappings of tumorinfiltrating lymphocytes (TILs) based on H&E images from 13 TCGA tumor types. These TIL maps are derived through computational staining using a convolutional neural network trained to classify patches of images. Affinity propagation revealed local spatial structure in TIL patterns and correlation with overall survival. TIL map structural patterns were grouped using standard histopathological parameters. These patterns are enriched in particular T cell subpopulations derived from molecular measures. TIL densities and spatial structure were differentially enriched among tumor types, immune subtypes, and tumor molecular subtypes, implying that spatial infiltrate state could reflect particular tumor cell aberration states. Obtaining spatial lymphocytic patterns linked to the rich genomic characterization of TCGA samples demonstrates one use for the TCGA image archives with insights into the tumor-immune microenvironment

The Regulatory Network of Natural Competence and Transformation of Vibrio cholerae

The human pathogen Vibrio cholerae is an aquatic bacterium frequently encountered in rivers, lakes, estuaries, and coastal regions. Within these environmental reservoirs, the bacterium is often found associated with zooplankton and more specifically with their chitinous exoskeleton. Upon growth on such chitinous surfaces, V. cholerae initiates a developmental program termed “natural competence for genetic transformation.” Natural competence for transformation is a mode of horizontal gene transfer in bacteria and contributes to the maintenance and evolution of bacterial genomes. In this study, we investigated competence gene expression within this organism at the single cell level. We provide evidence that under homogeneous inducing conditions the majority of the cells express competence genes. A more heterogeneous expression pattern was observable on chitin surfaces. We hypothesize that this was the case due to the heterogeneity around the chitin surface, which might vary extensively with respect to chitin degradation products and autoinducers; these molecules contribute to competence induction based on carbon catabolite repression and quorum-sensing pathways, respectively. Therefore, we investigated the contribution of these two signaling pathways to natural competence in detail using natural transformation assays, transcriptional reporter fusions, quantitative RT–PCR, and immunological detection of protein levels using Western blot analysis. The results illustrate that all tested competence genes are dependent on the transformation regulator TfoX. Furthermore, intracellular cAMP levels play a major role in natural transformation. Finally, we demonstrate that only a minority of genes involved in natural transformation are regulated in a quorum-sensing-dependent manner and that these genes determine the fate of the surrounding DNA. We conclude with a model of the regulatory circuit of chitin-induced natural competence in V. cholerae