QUANTUM DISSIPATION AND QUANTUM NOISE

We derive the exact action for a damped mechanical system ( and the special case of the linear oscillator) from the path integral formulation of the quantum Brownian motion problem developed by Schwinger and by Feynman and Vernon. The doubling of the phase-space degrees of freedom for dissipative systems and thermal field theories is discussed and the initial values of the doubled variables are related to quantum noise effects.Comment: This is a Tex file; To be published in Annals of Phys. (N.Y.) 238, 200 (1995

Analysis of the contributions of three-body potentials in the equation of state of 4He

The effect of three-body interatomic contributions in the equation of state of 4He are investigated. A recent two-body potential together with the Cohen and Murrell (Chem. Phys. Lett. 260, 371 (1996)) three-body potential are applied to describe bulk helium. The triple-dipole dispersion and exchange energies are evaluated subjected only to statistical uncertainties. An extension of the diffusion Monte Carlo method is applied in order to compute very small energies differences. The results show how the three-body contributions affects the ground-state energy, the equilibrium, melting and freezing densities.Comment: 18 pages, 3 figures, 4 table

On flavor conservation in weak interaction decays involving mixed neutrinos

In the context of quantum field theory (QFT), we compute the amplitudes of weak interaction processes such as $W^{+} \rightarrow e^{+} + \nu_{e}$ and $W^{+} \rightarrow e^{+} + \nu_{\mu}$ by using different representations of flavor states for mixed neutrinos. Analyzing the short time limit of the above amplitudes, we find that the neutrino states defined in QFT as eigenstates of the flavor charges lead to results consistent with lepton charge conservation. On the contrary, the Pontecorvo flavor states produce a violation of lepton charge in the vertex, which is in contrast with what expected at tree level in the Standard Model.Comment: 15 page

Online estimation of continuous gait phase for robotic transtibial prostheses based on adaptive oscillators

Continuous gait phase plays an important role in wearable robot control. This study focuses on the online estimation of continuous gait phase based on robotic transtibial prosthesis signals. First, we adopt the prosthetic foot deformation information to detect the heel strike as the start timing (reset 0 rad) of one gait cycle. Then we conduct the gait phase estimation based on adaptive oscillators using the prosthetic shank angle signal as input. Three transtibial amputees were recruited in this study and they walked on the treadmill at different speeds (slow, normal and fast) and on different ramps (10°, 5°, 0°, -5° and -10°) in the experiment. The root-meansquare error between online estimation result and ground truth gait phase is calculated. The maximum and minimum errors are 0.147 rad and 0.058 rad, and the corresponding ratios in one gait cycle are 2.34% and 0.92%. This study achieves good performance and provides an effective method to estimate the continuous gait phase, which will instruct robotic transtibial prosthesis control

Learning curve and global benchmark values of laparoscopic sleeve gastrectomy: results of first 100 cases of a newly trained surgeon in an Italian center of excellence

To evaluate whether the learning curve for sleeve gastrectomy could be completed after 50 cases. First 100 patients undergoing LSG under a newly trained laparoscopic surgeon were included in this study and divided into two groups of 50 consecutive patients each. Perioperative outcomes were compared to recently introduced global benchmarks. Short-term weight loss was calculated as Total Weight Loss Percent (%TWL) and complications were classified in accordance with the Clavien–Dindo classification. CUSUM analysis was performed for operative time and hospital stay. Mean preoperative age and BMI were 41.8 ± 10.3 years and 42.9 ± 5.4 kg/m2, respectively. Demographics and rate of patients with previous surgery were comparable preoperatively in the two groups. Mean operative time was 92.1 ± 19.3 min and hospital stay was 3.4 ± 0.6 days as per our standard protocol of discharge. Uneventful postoperative course was recorded in 93% of patients and only one case of staple line leak was registered in the first 50 cases (group 1). No statistical difference in BMI and %TWL was found between the two groups at any time of follow-up. Comparison between two groups showed a significant reduction in hospital stay and operative time after the first 50 LSGs (p < 0.05). LSG can be performed by newly trained surgeons proctored by senior tutors. At least 50 cases are needed to meet global benchmark cut-offs and few more cases may be required to reach the plateau of the learning curve

Flap fixation in preventing seroma formation after mastectomy: an updated meta-analysis

Seroma formation following mastectomy is one of the most experienced complications, with a very variable incidence ranging from 3 to 90%. In recent years, many publications have been realized to define an effective technique to prevent its formation and several approaches have been proposed. Given the potential of flap fixation in reducing seroma formation, we performed a meta-analysis of the literature to investigate the role of this approach as definitive gold standard in mastectomy surgery. Inclusion criteria regarded all studies reporting on breast cancer patients undergoing mastectomy with or without axillary lymph node dissection; studies that compared mastectomy with flap fixation to mastectomy without flap fixation were selected. Papers were eligible for inclusion if outcome was described in terms of seroma formation. As secondary outcome, also surgical site infection (SSI) was evaluated. The included studies were 12, involving 1887 female patients: 221/986 (22.41%) patients experienced seroma formation after flap fixation and 393/901 (43.61%) patients had this complication not receiving flap fixation, with a significant statistical difference between the two groups (OR = 0.267, p = 0.001, 95% CI 0.153, 0.464). About, SSI 59/686 (8.6%) in flap fixation group and 67/686 (9.7%) in patients without flap fixation, with no statistical differences between groups (OR = 0.59, p = 0.056, 95% CI 0.344, 1.013). The heterogeneity between included studies does not allow us to reach definitive conclusions but only to suggest the strong evaluation of this approach after mastectomy in seroma preventing and SSI reduction