Local electroexfoliation of graphene with a STM tip

Graphite surfaces can be manipulated by several methods to create graphene structures of different shapes and sizes. Scanning tunneling microscopy (STM) can be used to create these structures either through mechanical contact between the tip and the surface or through electro-exfoliation. In the latter, the mechanisms involved in the process of exfoliation with an applied voltage are not fully understood. Here we show how a graphite surface can be locally exfoliated in a systematic manner by applying an electrostatic force with a STM tip at the edge of a terrace, forming triangular flakes several nanometers in length. We demonstrate, through experiments and simulations, how these flakes are created by a two-step process: first a voltage ramp must be applied at the edge of the terrace, and then the tip must be scanned perpendicularly to the edge. Ab-initio electrostatic calculations reveal that the presence of charges on the graphite surface weakens the interaction between layers allowing for exfoliation at voltages in the same range as those used experimentally. Molecular dynamics simulations show that a force applied locally on the edge of a step produces triangular flakes such as those observed under STM. Our results provide new insights towards surface modification that can be extended to other layered materials

Topological bulk states and their currents

We provide evidence that, alongside topologically protected edge states, two-dimensional Chern insulators also support localized bulk states deep in their valence and conduction bands. These states manifest when local potential gradients are applied to the bulk, while all parts of the system remain adiabatically connected to the same phase. In turn, the bulk states produce bulk current transverse to the potential difference. This occurs even when the potential is always below the energy gap, where one expects only edge currents to appear. Bulk currents are topologically protected and behave as edge currents under an external influence, such as temperature or local disorder. Detecting topologically resilient bulk currents offers a direct means to probe the localized bulk states

Seeing topological edge and bulk currents in time-of-flight images

Here we provide a general methodology to directly measure the topological currents emerging in the optical lattice implementation of the Haldane model. Alongside the edge currents supported by gapless edge states, transverse currents can emerge in the bulk of the system whenever the local potential is varied in space, even if it does not cause a phase transition. In optical lattice implementations the overall harmonic potential that traps the atoms provides the boundaries of the topological phase that supports the edge currents, as well as providing the potential gradient across the topological phase that gives rise to the bulk current. Both the edge and bulk currents are resilient to several experimental parameters such as trapping potential, temperature, and disorder. We propose to investigate the properties of these currents directly from time-of-flight images with both short-time and long-time expansions

Increased circulating microRNAs miR-342-3p and miR-21-5p in natural sheep prion disease

Scrapie is a transmissible spongiform encephalopathy (TSE), or prion disease, of sheep and goats. As no simple diagnostic tests are yet available to detect TSEs in vivo, easily accessible biomarkers could facilitate the eradication of scrapie agents from the food chain. To this end, we analysed by quantitative reverse transcription PCR a selected set of candidate microRNAs (miRNAs) from circulating blood plasma of naturally infected, classical scrapie sheep that demonstrated clear scrapie symptoms and pathology. Significant scrapie-associated increase was repeatedly found for miR-342-3p and miR-21-5p. This is the first demonstration, to our knowledge, of circulating miRNA alterations in any animal suffering from TSE. Genome-wide expression studies are warranted to investigate the true depth of miRNA alterations in naturally occurring TSEs, especially in presymptomatic animals, as the presented study demonstrates the potential feasibility of miRNAs as circulating TSE biomarkers

3Dpaleo.net, una plataforma web de fósiles en 3D hiperrealista para fomentar la difusión y el conocimiento del patrimonio paleontológico

3Dpaleo.net es una plataforma web en fase de desarrollo que muestra modelos tridimensionales hiperrealistas y en alta definición de algunos de fósiles más emblemáticos del Museo de Ciencias Naturales de la Universidad de Zaragoza y del Museo del Jurásico de Asturias (MUJA), colaboradores de la primera fase del proyecto. Se trata de una iniciativa promovida por la empresa Paleoymás con el fin de explorar y explotar las posibilidades de las nuevas tecnologías, aplicándolas a la divulgación de la paleontología y a la mejora de técnicas expositivas y de difusión del conocimiento. 3Dpaleo.net facilita, a través de internet, la visualización de los fósiles y de algunos de sus detalles más interesantes. 3Dpaleo.net is a website, under development, that shows high definition hyperrealistic 3D models of some emblematic fossils of the museums that have collaborated in this first stage of the project: The Natural Sciences Museum of the University of Zaragoza and the Jurassic Museum of Asturias (MUJA). It is promoted by Paleoymás with the aim of exploring and developing the possibilities of new technologies, applying them to the popularization of paleontology and the improvement of both; expositive technics and knowledge sharing. 3Dpaleo.net helps through the internet to display fossils and some of their most interesting details

Noncoding RNA, antigenic variation, and the virulence genes of Plasmodium falciparum

Long non-coding RNAs (lncRNA) are being increasingly recognized as important regulators of gene expression. A recent paper in Genome Biology reports the identification of a lncRNA family in Plasmodium falciparum, the cause of the most deadly form of malaria, that may help to explain the mechanism of antigenic variation in virulence genes of this important pathogen

Dynamic Activation and Repression of the Plasmodium falciparum rif Gene Family and Their Relation to Chromatin Modification

The regulation of variant gene expression in Plasmodium falciparum is still only partially understood. Regulation of var genes, the most studied gene family involved in antigenic variation, is orchestrated by a dynamic pattern of inherited chromatin states. Although recent evidence pointed to epigenetic regulation of transcribed and repressed rif loci, little is known about specific on/off associated histone modifications of individual rif genes. To investigate the chromatin marks for transcribed and repressed rif loci, we cultivated parasites and evaluated the transcriptional status of chosen rif targets by qRT-PCR and performed ChIP assays using H3K9ac and H3K9me3 antibodies. We then monitored changes in the epigenetic patterns in parasites after several reinvasions and also evaluated the “poised” mark in trophozoites and schizonts of the same erythrocytic cycle by ChIP using H3K4me2 specific antibodies. Our results show that H3K9 is acetylated in transcribed rif loci and trimethylated or even unmodified in repressed rif loci. These transcriptional and epigenetic states are inherited after several reinvasions. The poised modification H3K4me2 showed a tendency to be more present in loci in trophozoites that upon progression to schizonts strongly transcribe the respective locus. However, this effect was not consistently observed for all monitored loci. While our data show important similarities to var transcription-associated chromatin modifications, the observed swiftly occurring modifications at rif loci and the absence of H3K9 modification point to a different dynamic of recruitment of chromatin modifying enzymes

Bench-to-bedside review : targeting antioxidants to mitochondria in sepsis

Peer reviewedPublisher PD

Coagulopathy as initial manifestation of concomitant celiac disease and cystic fibrosis: a case report

<p>Abstract</p> <p>Introduction</p> <p>Celiac disease and cystic fibrosis have many common manifestations, such as malabsorption, steatorrhea and growth failure, and were for many years recognized as one clinical entity. Since their recognition as two separate diseases, their co-existence in a patient has been described sporadically; around 20 cases have been described in the literature. Taking into consideration the incidences of the two diseases, the chance of them occurring together is one in 2,000,000 in the general population.</p> <p>Case presentation</p> <p>We describe the case of a five-year-old boy of Turkish ethnicity with both celiac disease and cystic fibrosis, who presented initially with a skin hemorrhage. The diagnosis of celiac disease was made with a positive serum anti-tissue transglutaminase antibody test and the presence of HLA-DQ2 heterodimer, and confirmed on histology with small intestinal villous atrophy. A positive sweat test confirmed the diagnosis of associated cystic fibrosis.</p> <p>To the best of our knowledge there has been no previous report of this rare presentation of associated celiac disease and cystic fibrosis.</p> <p>Conclusion</p> <p>The clinical significance of this case is the consideration of malabsorption with both celiac disease and cystic fibrosis in patients who present with unexplained coagulopathy.</p