Magic distances for flat bands in twisted bilayer graphene

Twisted bilayer graphene is known to host isolated and relatively flat bands near charge neutrality, when tuned to specific magic angles. Nonetheless, these rotational misalignments, lying below 1.1 degrees, result in long-period moir\'e crystals, whose anomalous electronic properties are hardly accessible to reliable atomistic simulations. Here, we present a map of differently stacked graphene sheets, at arbitrary rotation angles corresponding to precise interplanar distances, into an equivalence class represented by magic-angle twisted bilayer graphene. We determine the equivalence relation in the class within a continuum model, and extend its definition to a tight-binding approach. Then, we use density functional theory to suggest that the magic-angle physics may be characterized by costly computational strategies on a twisted bilayer geometry, with conveniently large stacking angles. Our results may pave the way for an ab initio characterization of the unconventional topological phases and related excitations, associated with currently observed low-energy quasi-flat bands

Tunable plasmons in regular planar arrays of graphene nanoribbons with armchair and zigzag-shaped edges

Recent experimental evidence for and the theoretical confirmation of tunable edge plasmons and surface plasmons in graphene nanoribbons have opened up new opportunities to scrutinize the main geometric and conformation factors, which can be used to modulate these collective modes in the infrared-to-terahertz frequency band. Here, we show how the extrinsic plasmon structure of regular planar arrays of graphene nanoribbons, with perfectly symmetric edges, is influenced by the width, chirality and unit-cell length of each ribbon, as well as the in-plane vacuum distance between two contiguous ribbons. Our predictions, based on time-dependent density functional theory, in the random phase approximation, are expected to be of immediate help for measurements of plasmonic features in nanoscale architectures of nanoribbon devicesC.V.G. acknowledges the financial support of the “Secretaria Nacional de Educación Superior, Ciencia, Tecnología e Innovación” (SENESCYT-ECUADOR

Assessing the sensitivity of inflation to economic activity

A number of academic studies suggest that from the mid-1990s onwards there were changes in the link between inflation and economic activity. However, it remains unclear the extent to which this phenomenon can be ascribed to a change in the structural relationship between inflation and output, as opposed to a change in the size and nature of the shocks hitting the economy. This paper uses a suite of models, such as time-varying VAR techniques, traditional macro models, as well as DSGE models, to investigate, for various European countries as well as for the euro area, the evolution of the link between inflation and resource utilization and its dependence on the nature and size of the shocks. Our analysis suggests that the relationship between inflation and activity has indeed been changing over time, while remaining positive, with the correlation peaking during recessions. Quantitatively, the link between output and inflation is found to be highly dependent on which type of shocks hit the economy: while, in general, all demand shocks to output imply a reaction of inflation of the same sign, the latter will be less pronounced when output fluctuations are driven by supply shocks. In addition, a sharp deceleration of activity, as opposed to a subdued but protracted slowdown, results in a swifter decline in inflation. Inflation exhibits a rather strong persistence, with a negative impact still visible three years after the initial shock. JEL Classification: E31, E32, E37demand shock, inflation response, Macro model, output growth, Phillips curve

Evaluation of efficacy and safety of new high-density dyes for chromovitrectomy

The purpose of this study is to evaluate the safety and efficacy of two novel heavy dyes for macular surgery: DoubledyneTM and TwinTM. One eye from each of 144 patients undergoing surgery for macular hole or macular pucker was included in the study. The eyes were randomly divided into two groups according to the dye used during surgery. Best correct visual acuity (BCVA), intraocular pressure (IOP) and retinal morphology assessed by ocular coherence tomography (OCT) were evaluated before and 1, 3, 6 and 12 months after surgery. Only one surgeon performed each operation and provided a score ranging from 1 (poor) to 10 (excellent) for quality of staining and comfort in surgery. Statistical analysis was carried out with SPSS to compare parameters before and after surgery and between the two groups. No statistical differences were recorded in quality of staining (p = 0.11), in surgery comfort (p = 0.17) and total time of surgery (p = 0.44) between the two groups. BCVA statistically improved and central macular thickness (CMT) statistically decreased after surgery in both groups (p < 0.05). No toxic dye-related complications or long-term ones affecting the retina were observed in either group. According to this data, although confirmation in further studies with larger populations and longer follow up is required, DoubledyneTM and TwinTM proved to be safe and effective dyes for macular surgery

Matera, storytelling e cinema

I destini dei luoghi sono in relazione con le narrazioni, e Matera ne è un esempio. Negli anni Cinquanta, insieme al paradigma della vergogna, inizia a prendere forma un nuovo immaginario dei Sassi, la magia di un mondo contadino arcaico e sconosciuto. L’inversione del giudizio porta al riconoscimento del valore universale dei Sassi nel 1993, e al titolo di Capitale Europea della Cultura per il 2019. Molta cinematografia, fino alle più recenti esperienze immersive, ha contribuito a costruirne l’immagine e i progetti di futuro

Near field behavior of SnO 2 particle-layer deposited on standard optical fiber by electrostatic spray pyrolysis method

We report the emergent optical near field profiles from standard single mode optical fibers on the cleaved end of which were deposited particle layers of SnO(2). The layers, composed of micron and sub-micron sized particles, were deposited by means of Electrostatic Spray Pyrolysis (ESP) technique. Powerful analytical tools such as Atomic Force Microscopy (AFM) and Scanning Near-field Optical Microscopy (SNOM) were used to obtain simultaneously the SnO(2) layers topography and the related optical near field intensity distribution, when the fiber-substrate is illuminated by a light radiation in NIR range. We show that isolated microstructures, positioned in correspondence of the fiber core, reveal highly unusual capability of locally enhancing the collected optical near field. The observed phenomenon leads to new concepts of fiber optic chemical sensors and in fiber microsystems as well

Highlights of the Keystone Symposium: sirtuins in metabolism, aging and disease

From February 12–16, 2012, leading members of the sirtuin scientific community assembled in Tahoe, CA to attend the Keystone Symposium “Sirtuins in Aging, Metabolism, and Disease.” It was a vibrant and lively meeting, and in the spirit of Keystone Symposia, both established sirtuin researchers and those new to the field enjoyed a unique opportunity to interact and exchange ideas

Production and characterization of random electrode sectorization in GEM foils

In triple-GEM detectors, the segmentation of GEM foils in electrically independent sectors allows reducing the probability of discharge damage to the detector and improving the detector rate capability; however, a segmented foil presents thin dead regions in the separation between two sectors and the segmentation pattern has to be manually aligned with the GEM hole pattern during the foil manufacturing, a procedure potentially sensitive to errors. We describe the production and characterization of triple-GEM detectors produced with an innovative GEM foil segmentation technique, the ``random hole segmentation'', that allows an easier manufacturing of segmented GEM foils. The electrical stability to high voltage and the gain uniformity of a random-hole segmented triple-GEM prototype are measured. The results of a test beam on a prototype assembled for the Phase-2 GEM upgrade of the CMS experiment are also presented; a high-statistics efficiency measurement shows that the random hole segmentation can limit the efficiency loss of the detector in the areas between two sectors, making it a viable alternative to blank segmentation for the GEM foil manufacturing of large-area detector systems