Symmetry breaking in a mechanical resonator made from a carbon nanotube

Nanotubes behave as semi-flexible polymers in that they can bend by a sizeable amount. When integrating a nanotube in a mechanical resonator, the bending is expected to break the symmetry of the restoring potential. Here we report on a new detection method that allows us to demonstrate such symmetry breaking. The method probes the motion of the nanotube resonator at nearly zero-frequency; this motion is the low-frequency counterpart of the second overtone of resonantly excited vibrations. We find that symmetry breaking leads to the spectral broadening of mechanical resonances, and to an apparent quality factor that drops below 100 at room temperature. The low quality factor at room temperature is a striking feature of nanotube resonators whose origin has remained elusive for many years. Our results shed light on the role played by symmetry breaking in the mechanics of nanotube resonators.Comment: manuscript and supplementary material, 7 figure

High-frequency nanotube mechanical resonators

We report on a simple method to fabricate high-frequency nanotube mechanical resonators reproducibly. We measure resonance frequencies as high as 4.2 GHz for the fundamental eigenmode and 11 GHz for higher order eigenmodes. The high-frequency resonances are achieved using short suspended nanotubes and by introducing tensile stress in the nanotube. These devices allow us to determine the coefficient of the thermal expansion of an individual nanotube, which is negative and is about -0.7E-5 1/K at room temperature. High-frequency resonators made of nanotubes hold promise for mass sensing and experiments in the quantum limit

Analyzing Medication Documentation in Electronic Health Records: Dental Students’ Self-Reported Behaviors and Charting Practices

The aim of this two-part study was to assess third- and fourth-year dental students’ perceptions, self-reported behaviors, and actual charting practices regarding medication documentation in axiUm, the electronic health record (EHR) system. In part one of the study, in fall 2015, all 125 third- and 85 fourth-year dental students at one U.S. dental school were invited to complete a ten-item anonymous survey on medication history-taking. In part two of the study, the EHRs of 519 recent dental school patients were randomly chosen via axiUm query based on age >21 years and the presence of at least one documented medication. Documentation completeness was assessed per EHR and each medication based on proper medication name, classification, dose/frequency, indication, potential oral effects, and correct medication spelling. Consistency was evaluated by identifying the presence/absence of a medical reason for each medication. The survey response rate was 90.6% (N=187). In total, 64.5% of responding students reported that taking a complete medication history is important and useful in enhancing pharmacology knowledge; 90.4% perceived it helped improve their understanding of patients’ medical conditions. The fourth-year students were more likely than the third-year students to value the latter (p=0.0236). Overall, 48.6% reported reviewing patient medications with clinic faculty 76-100% of the time. The respondents’ most frequently cited perceived barriers to medication documentation were patients’ not knowing their medications (68.5%) and, to a much lesser degree, axiUm limitations (14%). Proper medication name was most often recorded (93.6%), and potential oral effects were recorded the least (3.0%). Medication/medical condition consistency was 70.6%. In this study, most of the students perceived patient medication documentation as important; however, many did not appreciate the importance of all elements of a complete medication history, and complete medication documentation was low

Spin chain from membrane and the Neumann-Rosochatius integrable system

We find membrane configurations in AdS_4 x S^7, which correspond to the continuous limit of the SU(2) integrable spin chain, considered as a limit of the SU(3) spin chain, arising in N=4 SYM in four dimensions, dual to strings in AdS_5 x S^5. We also discuss the relationship with the Neumann-Rosochatius integrable system at the level of Lagrangians, comparing the string and membrane cases.Comment: LaTeX, 16 pages, no figures; v2: 17 pages, title changed, explanations and references added; v3: more explanations added; v4: typos fixed, to appear in Phys. Rev.

Persistence of Diophantine flows for quadratic nearly-integrable Hamiltonians under slowly decaying aperiodic time dependence

The aim of this paper is to prove a Kolmogorov-type result for a nearly-integrable Hamiltonian, quadratic in the actions, with an aperiodic time dependence. The existence of a torus with a prefixed Diophantine frequency is shown in the forced system, provided that the perturbation is real-analytic and (exponentially) decaying with time. The advantage consists of the possibility to choose an arbitrarily small decaying coefficient, consistently with the perturbation size.Comment: Several corrections in the proof with respect to the previous version. Main statement unchange

Mariposas em parreirais na região da Serra Gaúcha e informações sobre espécies com potencial para perfurar frutos.

Esta Circular Técnica apresenta informações sobre as mariposas registradas nos parreirais, bem como suas características morfológicas e biológicas, visando orientar técnicos e produtores quanto ao manejo que pode ser adotado nas áreas com presença desses insetos.bitstream/item/62488/1/cir089.pd

Motion of four-dimensional rigid body around a fixed point: an elementary approach. I

The goal of this note is to give the explicit solution of Euler-Frahm equations for the Manakov four-dimensional case by elementary means. For this, we use some results from the original papers by Schottky [Sch 1891], Koetter [Koe 1892], Weber [We 1878], and Caspary [Ca 1893]. We hope that such approach will be useful for the solution of the problem of $n$-dimensional top.Comment: LaTeX, 9 page