RESUMEN
Miniature batteries can accelerate the development of mobile electronics by providing sufficient energy to power small devices. Typical microbatteries commonly use thin-film inorganic electrodes based on Li-ion insertion reaction. However, they rely on the complicated thin-film synthesis method of inorganics containing many elements. Graphene, one atomic layer thick carbon sheet, has diverse physical and chemical properties and is compatible with conventional micron-scale device fabrication. Here, we study the use of chemical vapor deposition (CVD) grown monolayer graphene in a two-dimensional configuration, as a future Li-oxygen microbattery cathode. By maximizing the dissolution of discharge intermediates, we obtain 2610 Ah/ggraphene of capacity corresponding to 20% higher areal cathode energy density and 2.7 times higher cathode specific energy than that can be derived from the same volume or mass of conventional Li-ion battery cathode material. Furthermore, a clear observation on the discharge reaction on composite electrodes and their role in the charging reaction was made, thanks to the two-dimensional monolayer graphene Li-oxygen battery cathode. We demonstrate an easy integration of two-dimensional CVD graphene cathode into microscale devices by simply transferring or coating the target device substrate with flexible graphene layers. The ability to integrate and use monolayer graphene on arbitrary device substrates as well as precise control over a chemical derivation of the carbon interface can have a radical impact on future energy-storage devices.
RESUMEN
Magnetoresistance (MR), the change of a material's electrical resistance in response to an applied magnetic field, is a technologically important property that has been the topic of intense study for more than a quarter century. We report the observation of an unusual "butterfly"-shaped titanic angular magnetoresistance (AMR) in the nonmagnetic Dirac material, ZrSiS, which we find to be the most conducting sulfide known, with a 2-K resistivity as low as 48(4) nΩâ cm. The MR in ZrSiS is large and positive, reaching nearly 1.8 × 105 percent at 9 T and 2 K at a 45° angle between the applied current (I || a) and the applied field (90° is H || c). Approaching 90°, a "dip" is seen in the AMR, which, by analyzing Shubnikov de Haas oscillations at different angles, we find to coincide with a very sharp topological phase transition unlike any seen in other known Dirac/Weyl materials. We find that ZrSiS has a combination of two-dimensional (2D) and 3D Dirac pockets comprising its Fermi surface and that the combination of high-mobility carriers and multiple pockets in ZrSiS allows for large property changes to occur as a function of angle between applied fields. This makes it a promising platform to study the physics stemming from the coexistence of 2D and 3D Dirac electrons as well as opens the door to creating devices focused on switching between different parts of the Fermi surface and different topological states.
RESUMEN
El melanoma anorrectal es infrecuente, su clínica inespecífica y su diagnóstico tardío, acompañándose de pronóstico ominoso. Se reporta el caso de melanoma anorrectal. Mujer de 62 años con historia de baja de peso y masa rectal, estudio histológico evidencia melanoma anorrectal, realizándose cirugía respectiva y posterior radioterapia hipofraccionada. La clínica del melanoma anorrectal dificulta el diagnóstico, presentándose en edades propias de patologías más frecuentes y benignas como hemorroides. El tratamiento de elección es quirúrgico. Se recomienda un elevado índice de sospecha para manejo oportuno.
Anorrectal melanoma is rare, his clinic is unspecific and his diagnostic is late, accompanied by ominous prognosis. The case of anorrectal melanoma is reported. A 62 year old female presented weight loss and rectal mass, histology study showed melanoma anorrectal, resection surgery and radiotherapy hypofractionated were performed. Anorrectal melanoma clinical is a difficult diagnosis, this appears in ages where others diseases benign are more frequent, such as hemorrhoids. The treatment of choice is surgical. A high index of suspicion for timely management is recommended.