Tunneling States Research Articles

Development of a non-Gaussian copula Bayesian network for safety assessment of metro tunnel maintenance

The operation and maintenance of metro systems play a crucial role in urban development, with a focus on ensuring the serviceability and safety of metro tunnels. Accurate evaluation of the condition of these tunnel states requires investigating the complex interaction of multiple factors that impact their safety state. This study developed a hybrid model that integrates pair copula constructions (PCCs) and Bayesian networks (BN) to assess the safety state of metro tunnels, considering complex dependencies among these factors. First, key performance indicators (KPIs) were selected to assess tunnel safety, based on six failure modes. Then, an improved copula-based PC algorithm was employed to learn the non-Gaussian bayesian network model, which eliminated the normality assumption in the marginal densities of the KPIs. Finally, a combination of forward reasoning and GM(1,1) was utilized to predict the safety state of the metro tunnel in time series, facilitating the formulation of effective operation and maintenance plans. Furthermore, the proposed approach was applied to a real case study of the Wuhan metro system to demonstrate its effectiveness and applicability. The results highlighted the significant influence of some KPIs, such as convergence deformation, dislocation displacement, and stripping area, on metro tunnel safety. These KPIs emerged as key factors requiring focused attention in the operation and maintenance of metro tunnels.

Cost-effectiveness of selective internal radiation therapy with Y-90 resin microspheres for intermediate- and advanced-stage hepatocellular carcinoma in Brazil

AimsHepatocellular carcinoma (HCC) is a severe condition with poor prognosis that places a significant burden on patients, caregivers, and healthcare systems. Selective internal radiation therapy (SIRT) is a treatment available to patients with HCC which addresses some of the limitations of alternative treatment options. A cost-effectiveness analysis was undertaken into the use of SIRT using Y-90 resin microspheres for the treatment of unresectable intermediate- and late-stage HCC in Brazil.Materials and methodsA partitioned-survival model was developed, including a tunnel state for patients downstaged to receive treatments with curative intent. Sorafenib was the selected comparator, a common systemic treatment in Brazil and for which comparative evidence exists. Clinical data were extracted from published sources of pivotal trials, and effectiveness was measured in quality-adjusted life-years (QALYs) and life-years (LYs). The analysis was conducted from the Brazilian private payer perspective and a lifetime horizon was implemented. Comprehensive sensitivity analyses were conducted.ResultsLYs and QALYs were higher for SIRT with Y-90 resin microspheres versus sorafenib (0.27 and 0.20 incremental LYs and QALYs, respectively) and costs were slightly higher for SIRT (R$15,864). The base case incremental cost-effectiveness ratio (ICER) was R$77,602 per QALY. The ICER was mostly influenced by parameters defining the sorafenib overall survival curve and SIRT had a 73% probability of being cost-effective at a willingness-to-pay threshold of R$135,761 per QALY (3-times the per-capita gross domestic product in Brazil). Overall, sensitivity analyses confirmed the robustness of the results indicating that SIRT with Y-90 resin microspheres is cost-effective compared with sorafenib.LimitationsA rapidly evolving treatment landscape in Brazil and worldwide, and the lack of local data for some variables were the main limitations.ConclusionsSIRT with Y-90 resin microspheres is a cost-effective option compared with sorafenib in Brazil.

A Structure-Based Gaussian Expansion for Quantum Reaction Dynamics in Molecules: Application to Hydrogen Tunneling in Malonaldehyde.

We developed an approximate method for quantum reaction dynamics simulations, namely, a structure-based Gaussian (SBG) expansion approach, where SBG bases for the expansion of the wave function Ψ, expressed by a product of single-atom Cartesian Gaussians centered at the positions of respective nuclei, are mainly placed around critical structures on reaction pathways such as on the intrinsic reaction coordinate (IRC) through a transition state. In the present approach, the "pseudo-lattice points" at which SBGs are deployed are selected in a perturbative manner so as to make moderate the expansion length. We first applied the SBG idea to a two-dimensional quadruple-well model and obtained accurate tunneling splitting values between the lowest four states. We then applied it to hydrogen tunneling in malonaldehyde and achieved a tunneling splitting of 27.1 cm-1 with only 875 SBGs at the MP2/6-31G(d,p) level of theory, in good agreement with 25 cm-1 by the more elaborate multiconfiguration time-dependent Hartree method. Reasonable results were also obtained for singly and doubly deuterated malonaldehyde. We analyzed the tunneling states by utilizing expansion coefficients of individual SBGs and found that 40-45% of the SBGs in Ψ are nonplanar structures and SBGs away from the IRC contribute a little to hydrogen transfer.

Time reversed states in barrier tunneling

Tunneling, though a physical reality, is shrouded in mystery. Wave packets cannot be constructed under the barrier and group velocity cannot be defined. The tunneling particle can be observed on either sides of the barrier but its properties under the barrier has never been probed due to several problems related to quantum measurement. We show that there are ways to bypass these problems in mesoscopic systems and one can even derive an expression for the quantum mechanical current under the barrier. A general scheme is developed to derive this expression for any arbitrary system. One can use mesoscopic phenomenon to subject the expression to several theoretical and experimental cross checks. For demonstration we consider an ideal 1D quantum ring with Aharonov-Bohm flux $\Phi$, connected to a reservoir. It gives clear evidence that propagation occur under the barrier resulting in a current that can be measured non-invasively and theoretically cross checked. Time reversed states play a role but there is no evidence of violation of causality. The evanescent states are known to be largely stable and robust against phase fluctuations making them a possible candidate for device applications and so formalizing current under barrier is important.

CFD simulations of a semi-transverse ventilation system in a long tunnel

In the present work, a semi-transverse ventilation system in a long tunnel with a length of 4.9 km, as a complex case study, is numerically studied by performing a set of three-dimensional steady incompressible computational fluid dynamics (CFD) simulations. The ventilation system consisted of a ceiling duct connected to two axial fans at the ending portals, and a series of jet fans in the main tunnel for supporting airflow in the desired direction. To focus on what can and cannot be achieved in commissioning tests, the ventilation system’s performance in various scenarios is numerically evaluated with two different tunnel states; empty tunnel and complete traffic congestion with 1176 stationary vehicles – which is almost impossible to evaluate during a commissioning test. By considering two hypothetical locations for the extraction zone from the main tunnel (in a distance of 450 and 1000 m from one portal), it is shown that the required number of jet fans in a traffic condition drops from 57 for the first extraction location to 43 (25% decrease) when the ventilation system extracts from the second zone. We show that if only the close axial fan to the extraction zone is activated, the required number of jet fans reduces by 56% and 72% for the first and second extraction locations, respectively. This finding can provide a cheaper and easier controlling scenario for emergency ventilation.

Evaluation of the bone tunnel position and state of healing on second-look arthroscopy after pullout repair of medial meniscus posterior root tear during open-wedge high tibial osteotomy

BackgroundThe aim of the present study was to evaluate the outcome of pullout repair of medial meniscus posterior root tear during open-wedge high tibial osteotomy, including the bone tunnel position and the state of healing on second-look arthroscopy. MethodsThe cohort comprised 22 patients (six men, 16 women) who underwent arthroscopic root fixation by the transtibial pullout technique for medial meniscus posterior root tear during open-wedge high tibial osteotomy. The mean patient age was 63.7 years. The location of the tibial tunnel was assessed using a percentage-dependent method, and the location of a critical point was determined by two coordinates on CT. We defined the distance between the tibial tunnel center and the medial meniscal posterior root anatomic center as the TC-AC distance. The healing state was classified as complete, partial, or failed on second-look arthroscopy. Patients were categorized into those with complete or partial healing (group H) and those with failed healing (group F). The differences in the outcomes and characteristics of groups H and F were evaluated. ResultsTwelve and 10 knees were classified into groups H and F, respectively. The bone tunnel position was significantly more posterior in group H than in group F. The TC-AC distance was significantly shorter in group H than in group F. ConclusionsIn pullout repair of medial meniscus posterior root tear during open-wedge high tibial osteotomy, it was considered important to create a bone tunnel position more posterior to increase the healing rate on second-look arthroscopy.Level of evidence: Level Ⅳ.

The Georadar in the Evaluation of Reinforced Concrete Structures Affected by Corrosion

Ground Penetrating Radar (GPR) is a geophysical method that has several applications in the field of civil engineering, one of the largest fields being the evaluation of the technical state of the affected reinforced concrete structures by corrosion. In Cuba, this method has not been widely used as a non destructive test (NDT), largely due to the lack of knowledge of its potential in civil engineering. This article performs a critical analysis of some investigations in which the georadar is applied to evaluate the technical state of tunnels, bridges and buildings. The regulatory framework that protects the use of the georadar as NDT in the world and the applications that it has had so far in Cuba are addressed. The electromagnetic responses of the method to various injuries and causes that cause damage to reinforced concrete such as fractures, cavities, areas of humidity, chloride penetration and corrosion itself are also presented.

Traffic safety assessment and prediction under different lighting service states in road tunnels

The lighting service state of road tunnels has an important impact on traffic safety. To assess and predict traffic safety in road tunnels under different lighting service states, a traffic safety assessment system of road tunnels was innovatively established by using visual recognition clarity data from 300 field experiments, which uses the proposed traffic safety factor to assess the traffic safety of road tunnels under different lighting service states. Then, the Particle Swarm Optimization (PSO) algorithm is used to optimize the Back Propagation (BP) neural network, and a new traffic safety intelligent prediction method in road tunnels was constructed to predict the traffic safety factor under different lighting service states. The results of the study show that there is a negative correlation between simulated vehicle speed and visual clarity and a positive correlation between lighting attenuation and visual clarity. There is a negative correlation between the number of luminaire failures and the visual recognition clarity. When the lighting attenuation is below 70% or four and above luminaires fail, the lighting service states of road tunnels can seriously threaten traffic safety. The PSO-BP neural network model can accurately predict the traffic safety factor. The critical value of the traffic safety factor is 0.5965. This means that the lighting service state poses a threat to traffic safety in road tunnels when the traffic safety factor is lower than this value. The results of the study can provide the basis for developing a safe and low-carbon tunnel lighting maintenance program.

Effect of formic acid on O2 + OH˙CHOH → HCOOH + HO2 reaction under tropospheric condition: kinetics of cis and trans isomers.

Formic acid (HCOOH) is one of the highly abundant acids in the troposphere. It is important in the formation of atmospheric aerosols and impacts the acidity of rainwater. In the present scenario, the model chemistry of HCOOH(FA) sources and sinks is poorly understood. In this work, we apply quantum chemical methods coupled with advanced statistical rate theories to understand the production of FA and its catalytic behavior under tropospheric conditions. The potential energy surfaces (PES) for O2 + OH˙CHOH and O2 + OH˙CHOH(+FA) reactions were constructed using the CCSD(T)/6-311++G(3df,3pd)//M06-2X/6-311++G(3df,3pd) level and rate constants for the production of FA were predicted using Rice-Ramsperger-Kassel-Marcus (RRKM)/master equation (ME) simulation with Eckart tunnelling and canonical variational transition state theory (CVT) with small curvature tunnelling (SCT) between the temperature range of 200-320 K and pressure range of 0.001 to 10 bar. The reaction follows the formation of cis and trans intermediates followed by spontaneous decomposition via concerted HO2 elimination to form stable post intermediates, which then leads to the straight formation of cis and trans formic acid. The current study also helps understand the role of cis and trans contribution to the total rate constants. The results show that O2 + OH˙CHOH is dominated by both cis and trans isomers; however, the trans isomer plays a more important role in the catalytic reaction. This result is due to the formation of a strong hydrogen-bonded complex in the trans isomer, which is dominated by the enthalpy factor rather than the entropy factor. The results predict that the catalytic effect of FA on the O2 + OH˙CHOH reaction is important when the concentration of FA is not included in the calculations; however, it has no effect under tropospheric conditions, when the FA concentration is included in the calculation. As a result, the total effective reaction rate constants are smaller. This work provides experimental/theoretical confirmation of Franco et al. who predicted that methanediol is the precursor for the FA formation, resolving an open problem in the kinetics of the gas phase reaction. O2 + OH˙CHOH and O2 + OH˙CHOH(+FA) probably explain other diol systems, which can help explain the formation of other atmospheric acids that affect aerosol formation and cloud evolution.

Noise-dissipation Correlated Dynamics of a Double-well Bose-Einstein Condensate-reservoir System

Abstract: In this work, we study the dissipative dynamics of a double-well Bose-Einstein condensate (BEC) out-coupled to reservoir at each side of its trap. The sub-system comprises of a simple Bose-Hubbard model, where the interplay of atom-tunneling current and inter-particle interaction are the main quantum features. The contact with two separate heat baths causes dissipation and drives the system into a non-equilibrium state. The system is well described by the Generalized Quantum Heisenberg-Langevin equation. We considered two Markovian dissipative BEC systems based on (i) the mean-field model (MF), where the internal noise has been averaged out and (ii) the noise-correlated model (FDT). Physical quantities, such as population imbalance, coherence and entanglement of the system, are computed for the models. The two-mode BEC phases, such as the quantum tunneling state and the macroscopic quantum-trapping state, evolved into complicated dynamics by controlling the non-linear interaction and dissipation strengths. We found that many important quantum features produced by the noise-correlated FDT model are not captured by the mean-field model. Keywords: Double-well BEC, Dissipation, Noise, Markovian, Non-Markovian, Fixed points. PACS: 03.75 Lm, 03.65 Yz, 03.75 Gg, 05.

PD28 Cost-Effectiveness Of Selective Internal Radiation Therapy Using Y-90 Resin Microspheres For Unresectable Hepatocellular Carcinoma In Brazil

IntroductionHepatocellular cancer (HCC) is a severe condition with poor prognosis and a significant burden. Selective internal radiation therapy (SIRT) is recommended as an alternative treatment option to overcome some limitations of current treatments. This analysis estimated the cost-effectiveness of SIRT using Y-90 resin microspheres for the treatment of unresectable HCC in Brazil.MethodsThis study was conducted from the Brazilian payer perspective according to local guidelines, with a lifetime horizon. The use of SIRT in patients with intermediate- or advanced-stage HCC, without extrahepatic disease and ineligible to transarterial chemoembolization, was compared with sorafenib, the commonly used HCC systemic treatment in Brazil. A sensitivity analysis included the subgroup of patients with low tumour burden and preserved liver function.A partitioned-survival model was developed, which included a tunnel state for patients downstaged to receive a treatment with a curative intent such as liver surgery, transplantation or ablation. Survival curves, utilities and adverse events incidence were extracted from published sources of pivotal randomized control trials. Effectiveness of health interventions was measured in quality-adjusted-life-years (QALYs) and life-years (LYs). Local costs from Brazil were applied. Future costs and effects were discounted at five percent. A willingness-to-pay threshold of USD 53,936 was used, based on a 2017 review of healthcare technology adoption in Brazil.ResultsLYs and QALYs were higher for SIRT using Y-90 resin microspheres versus sorafenib (0.27 and 0.20 incremental LYs and QALYs, respectively) and costs were slightly higher for SIRT (USD 3,056 incremental costs). The incremental cost-effectiveness ratio (ICER) was USD 14,948 per QALY in the basecase.One-way and probabilistic sensitivity analyses confirmed the robustness of the analyses. Scenario analyses tested different model assumptions and reinforced the basecase results indicating that SIRT using Y-90 resin microspheres was highly likely to be cost-effective compared with sorafenib. Also, the ICER was lower in the subgroup compared with the overall population.ConclusionsSIRT using Y-90 resin microspheres represents a cost-effective option compared with sorafenib in Brazil.

Convolutional networks and transformers for intelligent road tunnel investigations

Visual inspections do not provide a reliable and objective assessment of the conservation state of road tunnels. Although direct tests might represent a valid survey approach, they would often lead to prohibitive costs if performed extensively. Therefore, indirect techniques, such as ground-penetrating radar (GPR), have become fundamental to supporting limited direct tests. The analysis of the GPR tunnel linings profiles is mainly hand-operated. It permits the detection of various tunnel linings defects, characterizing a tunnel’s global health state. In the present work, the authors developed an artificial intelligence (AI) based automatic road tunnel defects hierarchical classification framework to improve the efficiency of this powerful indirect surveying method. Adopting the most recent tools in image processing provided by the deep learning (DL) community, the authors proposed a convolutional neural network (CNN) with the acknowledged ResNet-50 architecture, initialized through the transfer learning method. For the sake of comparisons, the authors also adopted the state-of-art convolutional EfficientNet architecture. To further improve the proposed framework, the authors investigated how the bidimensional Fourier transform applied as a preprocessing procedure could affect the classification performances of the ResNet-50 model. Finally, to further enhance the classification performance, the state-of-art neural vision transformer (ViT) architecture has been adopted with the transfer learning approach to the currently proposed defects classification framework.

MODELING AND MONITORING OF STRUCTURAL SAFETY OF LONG-OPERATING UNDERGROUND STRUCTURES OF THE SEWAGE SYSTEM IN THE CONDITIONS OF INCREASING ANTHROPOGENIC ACTIONS IN ORDER TO PROVIDE SUSTAINABLE LIFECYCLE OF ENGINEERING INFRASTRUCTURE OF THE MEGACITY (THE EXPERIENCE OF ST. PETERSBURG)

Long-term operation in difficult engineering-geological conditions of unique underground sewage facilities creates the danger of violating their structural safety. A long-term study of the dynamics of changes in a technical state of large pumping stations and deep sewage tunnels made it possible to establish patterns of influence of intensive anthropogenic and dynamic actions on this process. The developed discrete and continuous diagnostic models of defect development in tunnel structures allow identifying potentially hazardous areas subjected to manifestation of critical failures and methods of their localization. On the basis of numerical modeling the boundaries of defect-free joint operation of the system “source of impact – geo-mass – sewage underground structure” have been determined. The geotechnical and structural calculations are used to simulate the interaction of the facilities with the soil environment and predict adaptive stress-strain control system parameters. With increasing external anthropogenic and dynamic impacts, modeling zones of urban areas with potentially dangerous sections of underground sewage facilities constitute the basis for development of regulatory documents on monitoring methods and safe development of the geotechnical infrastructure of a megacity.

A Tutorial on Time-Dependent Cohort State-Transition Models in R Using a Cost-Effectiveness Analysis Example.

In an introductory tutorial, we illustrated building cohort state-transition models (cSTMs) in R, where the state transition probabilities were constant over time. However, in practice, many cSTMs require transitions, rewards, or both to vary over time (time dependent). This tutorial illustrates adding 2 types of time dependence using a previously published cost-effectiveness analysis of multiple strategies as an example. The first is simulation-time dependence, which allows for the transition probabilities to vary as a function of time as measured since the start of the simulation (e.g., varying probability of death as the cohort ages). The second is state-residence time dependence, allowing for history by tracking the time spent in any particular health state using tunnel states. We use these time-dependent cSTMs to conduct cost-effectiveness and probabilistic sensitivity analyses. We also obtain various epidemiological outcomes of interest from the outputs generated from the cSTM, such as survival probability and disease prevalence, often used for model calibration and validation. We present the mathematical notation first, followed by the R code to execute the calculations. The full R code is provided in a public code repository for broader implementation.

A Proposal of a Cost-Effectiveness Modeling Approach for Heart Failure Treatment Assessment: Considering the Short- and Long-Term Impact of Hospitalization on Event Rates.

The rate of events such as recurrent heart failure (HF) hospitalization and death are known to dramatically increase directly after HF hospitalization. Furthermore, the number of HF hospitalizations is associated with irreversible long-term disease progression, which is in turn associated with increased event rates. However, cost-effectiveness models of HF treatments commonly fail to capture both the short- and long-term association between HF hospitalization and events. The aim of this study was to provide a decision-analytic model that reflects the short- and long-term association between HF hospitalization and event rates. Furthermore, we assess the impact of omitting these associations. We developed a life-time Markov cohort model to evaluate HF treatments, and modeled the short-term impact of HF hospitalization on event rates via a sequence of tunnel states, with transition probabilities following a parametric survival curve. The corresponding long-term impact was modeled via hazard ratios per HF hospitalization. We obtained baseline event rates and utilities from published literature. Subsequently, we assessed, for a hypothetical HF treatment, how omitting the modeled associations (through a simple two-state model) affects incremental quality-adjusted life-years (QALYs). We developed a model that incorporates both short- and long-term impacts of HF hospitalizations. Based on an assumed treatment effect of a 20% risk reduction for HF hospitalization (and associated reductions in all-cause mortality of 15%), omitting the short-term, the long-term, or both associations resulted in a 5%, 1%, and 22% decrease in QALYs gained, respectively. For both modeling components, i.e., the short- and long-term implications of HF hospitalization, the impact on incremental outcomes associated with treatment was substantial. Considering these aspects as proposed within this modeling approach better reflects the natural course of this progressive condition and will enhance the evaluation of future HF treatments.

A matrix completion algorithm for efficient calculation of quantum and variational effects in chemical reactions.

This work examines the viability of matrix completion methods as cost-effective alternatives to full nuclear Hessians for calculating quantum and variational effects in chemical reactions. The harmonic variety-based matrix completion (HVMC) algorithm, developed in a previous study [S. J. Quiton et al., J. Chem. Phys. 153, 054122 (2020)], exploits the low-rank character of the polynomial expansion of potential energy to recover vibrational frequencies (square roots of eigenvalues of nuclear Hessians) constituting the reaction path using a small sample of its entities. These frequencies are essential for calculating rate coefficients using variational transition state theory with multidimensional tunneling (VTST-MT). HVMC performance is examined for four SN2 reactions and five hydrogen transfer reactions, with each H-transfer reaction consisting of at least one vibrational mode strongly coupled to the reaction coordinate. HVMC is robust and captures zero-point energies, vibrational free energies, zero-curvature tunneling, and adiabatic ground state and free energy barriers as well as their positions on the reaction coordinate. For medium to large reactions involving H-transfer, with the sole exception of the most complex Ir catalysis system, less than 35% of total eigenvalue information is necessary for accurate recovery of key VTST-MT observables.

Abnormal specific heat at low temperatures and transport properties in Mg-Cu-Ag-Gd bulk metallic glass

We report the pronounced low-temperature specific-heat Cp anomalies in the Mg59.5Cu22.9Ag6.6Gd11 bulk metallic glass (BMG). The extrapolated electron's temperature coefficient γ0K is up to 681.8 mJ/(mol-Gd⋅Κ2) at 0 K, which is a heavy-fermion-like behavior. The low temperature specific heat indicates an enhancement of the conduction-electron effective mass m∗ below 7.5 K, suggesting that the Mg59.5Cu22.9Ag6.6Gd11 BMG is not free-electron-like solid. The excess specific heat in the Mg-based BMG is interpreted with tunneling states and spin glass state (magnetism) which are determined by subtracting electrons' and phonons' contribution to the specific heat below 12 K. The Boson peak (BP) temperature is located at 27 K, which is much higher than the reported values of other BMGs. And, a BP height of 0.047 mJ/(mol·K4) is obtained due to reduced free volume during copper mold casting with a slow cooling rate. The electrical resistivity was also investigated between 2 and 300 K, which has a negative temperature coefficient of resistivity (TCR) below 35 K (Kondo temperature, TK) and a positive value of 3.9 × 10−4/K above 35 K. There is a minimum at about 35 K for the electrical resistivity, which can be explained by the Kondo effect. For the resistivity above 35 K, it can be explained by the Faber-Ziman model due to the T-dependence change of structure factor.

Hydrogen four-level tunnel systems in substitutional body-centred cubic alloys

Abstract A brief account is provided of the main results of a study of the tunneling states of H trapped by substitutional (S) impurities in Nb, mainly consisting in anelasticity experiments. The phenomenology is rather complex when the concentration of S atoms is higher than a few parts per thousand, and various and contrasting interpretations are possible. The complication arises from the destruction of the symmetry of the S–H pair by the elastic interactions among the defects. The situation becomes, however, clear for an S content around 0.1 %, when the anelastic spectra reveal the relaxation processes due to the now nearly undistorted S–H complexes. In this case H delocalizes over four tetrahedral sites of a face of the cube containing the S atom, giving rise to a four-level tunnel system (FLS). The parameters of tunneling and coupling to phonons and electron excitations are similar to those found for the two-level system of H near an interstitial impurity, but new effects are found, due to the symmetry of the additional eigenstates of a centrosymmetric FLS.

(Sub-)millimeter-wave spectroscopy of gauche-propanal

A detailed analysis of (sub-)millimeter-wave spectra of the vibrational ground state (υ=0) combined with the energetically lowest excited vibrational state (υ24=1; aldehyde torsion) of gauche-propanal (g-C2H5CHO) up to 500GHz is presented. Both vibrational states, υ=0 and υ24=1, are treated with tunneling rotation interactions between their two respective tunneling states, which originate from two stable degenerate gauche-conformers; left- and right-handed configurations separated by a small potential barrier. Thanks to double-modulation double-resonance (DM-DR) measurements, important but weak c-type transitions connecting the tunneling states could be unambiguously assigned. In addition, Coriolis interaction as well as Fermi resonance between the two vibrational states needed to be taken into account to derive fits with experimental accuracy using Pickett’s SPFIT program in a reduced axis system (RAS). Based on the rotational analysis, the fundamental vibrational frequency ν24 of gauche-propanal is redetermined to 68.75037(30)cm−1.

Dimensional control of tunneling two-level systems in nanoelectromechanical resonators

Tunneling two level systems affect damping, noise and decoherence in a wide range of devices, including nanoelectromechanical resonators, optomechanical systems, and qubits. Theoretically this interaction is usually described within the tunneling state model. The dimensions of such devices are often small compared to the relevant phonon wavelengths at low temperatures, and extensions of the theoretical description to reduced dimensions have been proposed, but lack conclusive experimental verification. We have measured the intrinsic damping and the frequency shift in magnetomotively driven aluminum nanoelectromechanical resonators of various sizes at millikelvin temperatures. We find good agreement of the experimental results with a model where the tunneling two level systems couple to flexural phonons that are restricted to one or two dimensions by geometry of the device. This model can thus be used as an aid when optimizing the geometrical parameters of devices affected by tunneling two level systems.