Hyperfine and Spin-Orbit Coupling Effects on Decay of Spin-Valley States in a Carbon Nanotube.

The decay of spin-valley states is studied in a suspended carbon nanotube double quantum dot via the leakage current in Pauli blockade and via dephasing and decoherence of a qubit. From the magnetic field dependence of the leakage current, hyperfine and spin-orbit contributions to relaxation from blocked to unblocked states are identified and explained quantitatively by means of a simple model. The observed qubit dephasing rate is consistent with the hyperfine coupling strength extracted from this model and inconsistent with dephasing from charge noise. However, the qubit coherence time, although longer than previously achieved, is probably still limited by charge noise in the device.

Resonant Optomechanics with a Vibrating Carbon Nanotube and a Radio-Frequency Cavity.

In an optomechanical setup, the coupling between cavity and resonator can be increased by tuning them to the same frequency. We study this interaction between a carbon nanotube resonator and a radio-frequency tank circuit acting as a cavity. In this resonant regime, the vacuum optomechanical coupling is enhanced by the dc voltage coupling the cavity and the mechanical resonator. Using the cavity to detect the nanotube's motion, we observe and simulate interference between mechanical and electrical oscillations. We measure the mechanical ring down and show that further improvements to the system could enable the measurement of mechanical motion at the quantum limit.

Room-temperature exciton-polaritons with two-dimensional WS2.

Two-dimensional transition metal dichalcogenides exhibit strong optical transitions with significant potential for optoelectronic devices. In particular they are suited for cavity quantum electrodynamics in which strong coupling leads to polariton formation as a root to realisation of inversionless lasing, polariton condensation and superfluidity. Demonstrations of such strongly correlated phenomena to date have often relied on cryogenic temperatures, high excitation densities and were frequently impaired by strong material disorder. At room-temperature, experiments approaching the strong coupling regime with transition metal dichalcogenides have been reported, but well resolved exciton-polaritons have yet to be achieved. Here we report a study of monolayer WS2 coupled to an open Fabry-Perot cavity at room-temperature, in which polariton eigenstates are unambiguously displayed. In-situ tunability of the cavity length results in a maximal Rabi splitting of hΩRabi = 70 meV, exceeding the exciton linewidth. Our data are well described by a transfer matrix model appropriate for the large linewidth regime. This work provides a platform towards observing strongly correlated polariton phenomena in compact photonic devices for ambient temperature applications.

Modeling Variability in the Progression of Huntington's Disease A Novel Modeling Approach Applied to Structural Imaging Markers from TRACK-HD.

We present a novel, general class of disease progression models for Huntington's disease (HD), a neurodegenerative disease caused by a cytosine-adenine-guanine (CAG) triplet repeat expansion on the huntingtin gene. Models are fit to a selection of structural imaging markers from the TRACK 36-month database. The models are of mixed effects type and should be useful in predicting any continuous marker of HD state as a function of age and CAG length (the genetic factor that drives HD pathology). The effects of age and CAG length are modeled using flexible regression splines. Variability not accounted for by age, CAG length, or covariates is modeled using terms that represent measurement error, population variability (random slopes/intercepts), and variability due to the dynamics of the disease process (random walk terms). A Kalman filter is used to estimate variances of the random walk terms.

Nanoscale control of graphene electrodes.

Single layer graphene nano-gaps are fabricated by applying the method of feedback-controlled electroburning to notched ribbon devices, which are plasma etched from CVD grown graphene that is wet-transferred onto pre-patterned metal electrodes. Electrical and structural characterizations show that nanometer size gaps form at the center of the notch. We have processed a total number of 1079 devices using this method with a fabrication yield of 71%. Our results demonstrate precise control over the size and position of the nano-gaps, and open up the possibility of graphene electrodes for large-scale integrated molecular devices.

Fabrication and characterization of fully flattened carbon nanotubes: a new graphene nanoribbon analogue.

Graphene nanoribbons (GNR) are one of the most promising candidates for the fabrication of graphene-based nanoelectronic devices such as high mobility field effect transistors (FET). Here, we report a high-yield fabrication of a high quality another type of GNR analogue, fully flattened carbon nanotubes (flattened CNTs), using solution-phase extraction of inner tubes from large-diameter multi-wall CNTs (MWCNTs). Transmission electron microscopy (TEM) observations show that flattened CNTs have width of typically 20 nm and a barbell-like cross section. Measurements of the low-bias conductance of isolated flattened CNTs as a function of gate voltage shows that the flattened CNTs display ambipolar conduction which is different from those of MWCNTs. The estimated gap based on temperature dependence of conductivity measurements of isolated flattened CNTs is 13.7 meV, which is probably caused by the modified electronic structure due to the flattening.

The safety and efficacy of short course (5-day) moxifloxacin vs. azithromycin in the treatment of patients with acute exacerbation of chronic bronchitis.

Chronic bronchitis is common among adults and infectious exacerbations contribute considerably to morbidity and mortality. We aimed to compare the safety and efficacy of moxifloxacin to azithromycin for the treatment of patients with acute exacerbations of chronic bronchitis (AECB) of suspected bacterial origin. Between October 1998 and April 1999, 567 patients with AECB were enrolled at 37 centers across the United States and Canada of which 280 (49%) had acute bacterial exacerbation of chronic bronchitis (i.e. pretherapy pathogen). Patients were randomized to either oral moxifloxacin 400 mg administered once daily for 5 days or azithromycin for 5 days (500 mg qd x 1, then 250 mg qd x 4). For the purpose of study blinding, all patients received encapsulated tablets. The main outcome measure was clinical response at the test-of-cure visit (14-21 days post-therapy). Secondary measures included bacteriologic response and a time-course of bacteriological eradication (one center only). Three patient populations were analysed for efficacy: clinically-valid, microbiologically-valid (i.e. those with a pretherapy pathogen), and intent-to-treat (i.e. received at least one dose of study drug). For the efficacy-valid group, clinical response at the test-of-cure visit was 88% for patients in each treatment group. In 237 microbiologically-valid patients, corresponding clinical resolution rates were 88% for 5-day moxifloxacin vs. 86% for 5-day azithromycin. Bacteriological eradication rates at the end of therapy were 95% for 5-day moxifloxacin and 94% for the azithromycin group. Corresponding eradication rates at the test-of-cure visit were 89% and 86%, respectively. Of note, eradication rates at test-of-cure for Haem. philos influenzae and H. parainfluenzae for moxifloxacin were 97% and 88% compared to 83% and 62% respectively for azithromycin. Among 567 intent-to-treat patients (283 moxifloxacin and 284 azithromycin), drug-related events were reported for 22% and 17%, respectively. Diarrhea and nausea were the most common drug-related events reported in each treatment group. Moxifloxacin 400 mg once daily for 5 days was found to be clinically and bacteriologically equivalent to 5-day azithromycin for the treatment of AECB of proven bacterial etiology. Given its excellent in-vitro activity, especially against antibiotic-resistant respiratory pathogens, and its acceptable safety profile, moxifloxacin should be considered an effective alternative therapy for patients with AECB of suspected bacterial origin.

Predictors of fecundability and conception waits among the Dogon of Mali.

Surprisingly little is known about the mechanisms that underlie variation in female fertility in humans. Data on this topic are nonetheless vital to a number of pragmatic and theoretical enterprises, including population planning, infertility treatment and prevention, and evolutionary ecology. Here we study female fertility by focusing on one component of the interbirth interval: the waiting time to conception during menstrual cycling. Our study population is a Dogon village of 460 people in Mali, West Africa. This population is pronatalist and noncontracepting. In accordance with animist beliefs, the women spend five nights sleeping at a menstrual hut during menses. By censusing the women present at the menstrual huts in the study village on each of 736 consecutive nights, we were able to monitor women's conception waits prospectively. Hormonal profiles confirm the accuracy of the data on conception waits obtained from the menstrual hut census (Strassmann [1996], Behavioral Ecology 7:304-315). Using survival analysis, we identified significant predictors of the waiting time to conception: wife's age (years), husband's age (< 35, 35-49, > 49 years), marital duration (years), gravidity (number of prior pregnancies), and breast-feeding status. Additional variables were not significant, including duration of postpartum amenorrhea, sex of the last child, nutritional status, economic status, polygyny, and marital status (fiancée vs. married). We fit both continuous and discrete time survival models, but the former appeared to be a better choice for these data.

PIP: Female fertility in the Dogon village of Sangui, Mali, was studied by focusing upon the waiting time to conception during menstrual cycling among 50 women aged 16-41 years over 736 consecutive days. Sangui had a pronatalist and noncontracepting population of 460 as of January 1988. In accordance with animist beliefs, the women of Sangui spend 5 nights sleeping at a menstrual hut during menses. The women's conception waits were monitored prospectively by surveying the women present at the two menstrual huts in the study village on each of 736 consecutive nights from July 1986 to July 1988. 33 of 50 women observed became recognizably pregnant during the study, while 25 women cycled without becoming pregnant. Hormonal profiles confirm the accuracy of the data on conception waits obtained from the menstrual hut census. The following factors were significant predictors in the continuous time model of the waiting time to conception: wife's age, husband's age, marital duration, gravidity, and breast-feeding status. Additional variables were not significant, including duration of postpartum amenorrhea, sex of the last child, nutritional status, economic status, polygyny, and marital status.

Information effect on the perception of pain during electromyography.

Pain during the performance of electromyography (EMG) is an important clinical problem because pain distresses the patient and can interfere with diagnostic accuracy. We hypothesized that anxiety and pain perception associated with EMG would decrease if patients received written material describing the EMG before examination. Forty-two subjects received written material and 30 did not. Information before the test significantly decreased pain perception for women during the nerve conduction studies (p = .008), but not during the needle examination. A similar effect was not identified for the men. Other results indicate that women perceive the test as more painful than do men, older subjects perceive more pain and experience greater anxiety than do younger subjects, and all subjects perceive greater pain during the performance of (concentric, bipolar) needle electromyography than during the nerve conduction studies.