Dynamic manipulation of mechanical resonators in the high amplitude regime through optical backaction

Cavity optomechanics enables active manipulation of mechanical resonators through backaction cooling and amplification. This ability to control mechanical motion with retarded optical forces has recently spurred a race towards realizing a mechanical resonator in its quantum ground state. Here, instead of quenching optomechanical motion, we demonstrate high amplitude operation of nanomechanical resonators by utilizing a highly efficient phonon generation process. In this regime, the nanomechanical resonators gain sufficient energy from the optical field to overcome the large energy barrier of a double well potential, leading to nanomechanical slow-down and zero frequency singularity, as predicted by early theories . Besides fundamental studies and interests in parametric amplification of small forces, optomechanical backaction is also projected to open new windows for studying discrete mechanical states, and to foster applications. Here we realize a non-volatile mechanical memory element, in which bits are written and reset via optomechanical backaction by controlling the mechanical damping across the barrier. Our study casts a new perspective on the energy dynamics in coupled mechanical resonator - cavity systems and enables novel functional devices that utilize the principles of cavity optomechanics.Comment: 22 pages, 5 figure

The CHAI libraries

Abstract. In this paper we present CHAI, a set of haptic/graphics C++ libraries that were developed in the last years by a varied group of researchers. The CHAI libraries allow both high level and low level programming of haptic applications. Users that are not interested in implementation details can easily build visual-haptic scenes using a large set of pre-implemented algorithms. However, differently from other existing haptic libraries, the CHAI libraries allow users to tweak with low level details, such as changing the control algorithms for supported devices or adding new custom devices. CHAI is a growing project, one featuring the efforts of many researchers around the world. A steering committee will periodically review any proposed addition to the libraries and publish new extended releases. Some demos created using CHAI, as well as the main features of the libraries, will be demonstrated during Eurohaptics demo session. In such occasions CD-ROMs containing the latest release of CHAI, as well as its documentation, will be freely handed out to anyone who is interested.

Efficacy and safety of clopidogrel after PCI with stenting in patients on oral anticoagulants with acute coronary syndrome

Aims: To evaluate crude cardiovascular risk in patients with acute coronary syndrome (ACS) who are on oral anticoagulants (OAC) after percutaneous coronary intervention with stents (PCI-S) and also to evaluate if the patients on OAC after PCI-S benefit from clopidogrel. less thanbrgreater than less thanbrgreater thanMethods and results: Data from RIKS-HIA and SCAAR on patients admitted to coronary care units 1997 to 2005, undergoing PCI-S (n=27,972), were evaluated. OAC were prescribed to 4.2% (n=1,183) of the patients and they had higher crude 1-year mortality than the non-OAC group, (3.6% [n=421 vs. 1.5% [n= 413], p=0.008), but after adjusting for pre-treatment patient characteristics there were no significant difference in 1-year mortality (adjusted risk ratio [adj. RR] 0.82 [95% CI 0.58-1.16]). Of patients on OAC, 56% (n=659) were also on clopidogrel at discharge. Incidence of death or myocardial infarction (MI) within one year did not differ between the clopidogrel and non-clopidogrel group, adj. RR 0.93 (95% Cl 0.65-1.34). Triple therapy (OAC, clopidogrel plus aspirin) was associated with four times higher risk of any bleeding than OAC plus aspirin, adj. RR 4.27 (95% Cl 1.2-15.1) but a lower incidence of death or MI than OAC plus clopidogrel adj. RR 0.63 (95% Cl 0.40-0.99) less thanbrgreater than less thanbrgreater thanConclusions: Patients discharged on OAC after PCI-S in ACS have higher crude 1-year mortality than patients not on OAC, largely explained by age and comorbidities. Adding clopidogrel is not associated with lower incidence of death or MI at one year. Triple therapy is associated with higher risk of any bleeding than OAC plus aspirin but lower risk of death or MI than OAC plus clopidogrel.</p

Relationships among patient characteristics, irradiation treatment planning parameters, and treatment toxicity of acute radiation dermatitis after breast hybrid intensity modulation radiation therapy.

To evaluate the relationships among patient characteristics, irradiation treatment planning parameters, and treatment toxicity of acute radiation dermatitis (RD) after breast hybrid intensity modulation radiation therapy (IMRT). The study cohort consisted of 95 breast cancer patients treated with hybrid IMRT. RD grade ≥2 (2+) toxicity was defined as clinically significant. Patient characteristics and the irradiation treatment planning parameters were used as the initial candidate factors. Prognostic factors were identified using the least absolute shrinkage and selection operator (LASSO)-based normal tissue complication probability (NTCP) model. A univariate cut-off dose NTCP model was developed to find the dose-volume limitation. Fifty-two (54.7%) of ninety-five patients experienced acute RD grade 2+ toxicity. The volume of skin receiving a dose >35 Gy (V35) was the most significant dosimetric predictor associated with RD grade 2+ toxicity. The NTCP model parameters for V35Gy were TV50 = 85.7 mL and γ50 = 0.77, where TV50 was defined as the volume corresponding to a 50% incidence of complications, and γ50 was the normalized slope of the volume-response curve. Additional potential predictive patient characteristics were energy and surgery, but the results were not statistically significant. To ensure a better quality of life and compliance for breast hybrid IMRT patients, the skin volume receiving a dose >35 Gy should be limited to 35 Gy should follow sparing tolerance and the inherent patient characteristics should be considered