Single-photon sources based on stepwise optimized binary-tree multiplexers.

We propose a spatially multiplexed single-photon source where the structure of the applied binary-tree multiplexer is optimized systematically during its construction. Along the building procedure of this type of multiplexer, the position of a binary photon router appended to the tree in a step of the expansion is determined by taking into account the current achievable single-photon probability of the source. The method chooses the position where this probability is maximal. We determine the stepwise optimized binary-tree multiplexers for experimentally realizable values of the loss parameters, and for a fixed number of routers. The method is scalable, that is, it is possible to determine the multiplexer with an optimal structure for any number of photon routers. We show that single-photon sources based on stepwise optimized binary-tree multiplexers yield higher single-photon probabilities than single-photon sources based on any spatial multiplexer types discussed in the literature thus far in the considered ranges of the loss parameters.

Even and Odd Cat States of Two and Three Qubits in the Probability Representation of Quantum Mechanics.

We derive the probability representation of even and odd cat states of two and three qubits. These states are even and odd superpositions of spin-1/2 eigenstates corresponding to two opposite directions along the z axis. The probability representation of even and odd cat states of an oscillating spin-1/2 particle is also discussed. The exact formulas for entangled probability distributions describing density matrices of all these states are obtained.

Single-photon sources based on incomplete binary-tree multiplexers with optimal structure.

We consider novel types of spatially multiplexed single-photon sources based on output-extended incomplete binary-tree multiplexers containing general asymmetric routers where the construction of the multiplexers takes into account the total transmission efficiencies of the multiplexer arms at which a novel router can be added to the system. After selecting the multiplexer that outperforms the others, we identify the ranges of the loss parameters for which the application of the selected multiplexer leads to single-photon sources with higher single-photon probabilities and lower multiphoton noise than that can be achieved by using asymmetric multiplexers. We show that using the selected multiplexer is especially advantageous in the case of single-mode sources characterized by thermal statistics of the input photon pairs. We also reveal that the application of this multiplexer yields high performance single-photon sources even for suboptimal system sizes that is a typical situation in current experiments.

Spatially multiplexed single-photon sources based on incomplete binary-tree multiplexers.

We propose two novel types of spatially multiplexed single-photon sources based on incomplete binary-tree multiplexers. The incomplete multiplexers are extensions of complete binary-tree multiplexers, and they contain incomplete branches either at the input or at the output of them. We analyze and optimize these systems realized with general asymmetric routers and photon-number-resolving detectors by applying a general statistical theory introduced previously that includes all relevant loss mechanisms. We show that the use of any of the two proposed multiplexing systems can lead to higher single-photon probabilities than that achieved with complete binary-tree multiplexers. Single-photon sources based on output-extended incomplete binary-tree multiplexers outperform those based on input-extended ones in the considered parameter ranges, and they can in principle yield single-photon probabilities higher than 0.93 when they are realized by state-of-the-art bulk optical elements. We show that the application of the incomplete binary-tree approach can significantly improve the performance of the multiplexed single-photon sources for suboptimal system sizes that is a typical situation in current experiments.

Use of lumen-apposing metal stents (LAMS) in the management of gastro jejunostomy stricture following Roux-en-Y Gastric Bypass for obesity: a prospective series.

BACKGROUND: Chronic strictures following Roux-en-Y Gastric Bypass (RYGB) are a troublesome complication that can lead to significant morbidity. The use of stents has been described but the need for X-ray and risk of migration have meant limited use in the management of these strictures. Lumen apposing metal stents (LAMS) have traditionally been used for management of pancreatic pseudocysts. They don't require X-ray and are easy to deploy with a short learning curve. This paper explores the use of LAMS to treat post RYGB strictures and explores their safety and efficacy. METHODS: A prospective study over a 4-year period looking at 14 patients with post RYGB strictures. These patients were privately insured patients operated within a tertiary Private facility. The patients were followed up for between 1 and 3 years. We have prospectively collected data on the efficacy and safety of LAMS in these patients. Patients were followed up until stent removal or definitive surgery to correct a stricture. RESULTS: 421 patients underwent RYGB in the study period. 14 (3.3%) of these patients developed a stricture that resulted in insertion of LAMS. There was no immediate complications and 12 patients had complete resolution of their stricture. There were no reoperations due to migration related issues although a migration rate of 19% was noted. 2 patients required surgery to correct refractory strictures not relieved by a LAMS stent, both of these were strictures associated with marginal ulceration of the gastro jejunostomy. CONCLUSION: LAMS are a safe and effective method to manage post RYGB strictures. They have a high rate of resolution of strictures and can be safely deployed across strictures with no immediate complication. Migration does still appear to be a problem, however, does not appear to affect patient outcome or increase morbidity. Insertion is straightforward and doesn't appear to be associated with a long learning curve.

Comparison of Training Intensity Patterns for Cardiorespiratory, Speed, and Strength Exercise Programs.

Vetter, RE, Yu, H, Foose, AK, Adam, PJ, and Dodd, RK. Comparison of training intensity patterns for cardiorespiratory, speed, and strength exercise programs. J Strength Cond Res 31(12): 3372-3395, 2017-Designing effective exercise training programs is important for novice, regular, and elite individuals desiring improvements in physical fitness and performance outcomes without experiencing deleterious physiological or performance effects. The purpose of this research was to understand the impact of training intensity on the effectiveness of training program outcomes. Synthesized analyses of 31 studies provided an overall magnitude for the impact of training program intensity on effect size (ES). Meta-analyses were performed using meta-regression models to assess the impact of training program intensity and the other moderators of training frequency, training weeks, age, ability level, and type of physical exercise training. Inclusion criteria were (a) pretest and posttest outcomes, group size, and mean and SDs were given, (b) only human participants, age 17 or older, and healthy being free of disease, injury, or pregnancy, (c) no supplements or dietary interventions were used, (d) a minimum 4-week training intervention was used, and (e) training protocols included training intensity as its focus. Of the research reviewed, there were 31 studies representing 292 cases used to calculate ES, which met the inclusion criteria. Training frequency, training weeks, age, and ability level did not consistently affect the effectiveness of the different training programs. Intensity level influenced ES across the types of physical training programs: cardiorespiratory, muscular strength, or speed. An aggregated model had a curvilinear effect on training programs with an estimated critical average value of 74%. Muscular strength training using intensities greater than estimated 87.29% resulted in diminishing returns.

Maximum information measurement for qubit states.

We determine the optimal measurement that maximizes the average information gain about the state of a qubit system. The qubit is prepared in one of two known states with known prior probabilities. To treat the problem analytically we employ the formalism developed for the maximum confidence quantum state discrimination strategy and obtain the POVM which optimizes the information gain for the entire parameter space of the system. We show that the optimal measurement coincides exactly with the minimum-error quantum measurement only for two pure states, or when the two states have the same Bloch radius or they are on the same diagonal of the Bloch disk.

Implementing no-signaling correlations as a service.

We deal with no-signaling correlations that include Bell-type quantum nonlocality. We consider a logical implementation using a trusted central server with encrypted connections to clients. We show that in this way it is possible to implement two-party no-signaling correlations in an asynchronous manner. While from the point of view of physics our approach can be considered as the computer emulation of the results of measurements on entangled particles, from the software engineering point of view it introduces a primitive in communication protocols that can be capable of coordinating agents without revealing the details of their actions. We present an actual implementation in the form of a Web-based application programming interface (RESTful Web API). We demonstrate the use of the API via the simple implementation of the Clauser-Horne-Shimony-Holt game.

Predicting choice behaviour in economic games using gaze data encoded as scanpath images.

Eye movement data has been extensively utilized by researchers interested in studying decision-making within the strategic setting of economic games. In this paper, we demonstrate that both deep learning and support vector machine classification methods are able to accurately identify participants' decision strategies before they commit to action while playing games. Our approach focuses on creating scanpath images that best capture the dynamics of a participant's gaze behaviour in a way that is meaningful for predictions to the machine learning models. Our results demonstrate a higher classification accuracy by 18% points compared to a baseline logistic regression model, which is traditionally used to analyse gaze data recorded during economic games. In a broader context, we aim to illustrate the potential for eye-tracking data to create information asymmetries in strategic environments in favour of those who collect and process the data. These information asymmetries could become especially relevant as eye-tracking is expected to become more widespread in user applications, with the seemingly imminent mass adoption of virtual reality systems and the development of devices with the ability to record eye movement outside of a laboratory setting.

Variational properties of the discrete variable representation: discrete variable representation via effective operators.

A variational finite basis representation/discrete variable representation (FBR/DVR) Hamiltonian operator has been introduced. By calculating its matrix elements exactly one obtains, depending on the choice of the basis set, either a variational FBR or a variational DVR. The domain of grid points on which the FBR/DVR is variational has been shown to consist of the subsets of the set of grid points one obtains by diagonalizing commuting variational basis representations of the coordinate operators. The variational property implies that the optimal of the subsets of a fixed number of points, i.e., the subset which gives the possible highest accuracy eigenpairs, gives the DVR of the smallest trace. The symmetry properties of the variational FBR/DVR Hamiltonian operator are analyzed and methods to incorporate symmetry into FBR/DVR calculations are discussed. It is shown how the Fourier-basis FBR/DVR suitable to solving periodic systems arise within the theory presented. Numerical examples are given to illustrate the theoretical results. The use of variational effective Hamiltonian and coordinate operators has been instrumental in this study. They have been introduced in a novel way by exploiting quasi-Hermiticity.

Effectiveness of providing university students with a mindfulness-based intervention to increase resilience to stress: 1-year follow-up of a pragmatic randomised controlled trial.

BACKGROUND: There is concern that increasing demand for student mental health services reflects deteriorating student well-being. We designed a pragmatic, parallel, single-blinded randomised controlled trial hypothesising that providing mindfulness courses to university students would promote their resilience to stress up to a year later. Here we present 1-year follow-up outcomes. METHODS: University of Cambridge students without severe mental illness or crisis were randomised (1:1, remote software-generated random numbers), to join an 8-week mindfulness course adapted for university students (Mindfulness Skills for Students (MSS)), or to mental health support as usual (SAU). RESULTS: We randomised 616 students; 53% completed the 1-year follow-up questionnaire. Self-reported psychological distress and mental well-being improved in the MSS arm for up to 1 year compared to SAU (p<0.001). Effects were smaller than during the examination period. No significant differences between arms were detected in the use of University Counselling Service and other support resources, but there was a trend for MSS participants having milder needs. There were no differences in students' workload management; MSS participants made more donations. Home practice had positive dose-response effects; few participants meditated. No adverse effects related to self-harm, suicidality or harm to others were detected. CONCLUSION: Loss to follow-up is a limitation, but evidence suggests beneficial effects on students' average psychological distress that last for at least a year. Effects are on average larger at stressful times, consistent with the hypothesis that this type of mindfulness training increases resilience to stress. TRIAL REGISTRATION NUMBER: ACTRN12615001160527.

Axillary Lymph Nodes Hypermetabolism After BNT162b2 mRNA COVID-19 Vaccination in Cancer Patients Undergoing 18F-FDG PET/CT: A Cohort Study.

PURPOSE: Recognition of the pattern of FDG uptake in hypermetabolic axillary lymph nodes (HALs) and association with recent messenger RNA (mRNA) vaccination are important to prevent patient anxiety and further needless examinations or costly biopsies in cancer patients. MATERIALS AND METHODS: This study was a retrospective cohort study in a single tertiary care institution. We investigate the occurrence and pattern of HAL on FDG PET/CT scans from 650 consecutive cancer patients with recent BNT162b2 mRNA COVID-19 vaccination. RESULTS: Between December 20, 2020, and February 8, 2021, 650 patients (351 female patients [54%]; mean age, 68.9 years) had recent mRNA COVID-19 vaccination and an FDG PET/CT scan. HALs were found in 57 (14.5%) of 394 patients (95% confidence interval [CI], 10.9%-18.7%) 12.3 ± 5.9 (1-22) days after dose 1 and in 111 (43.3%) of 256 patients (95% CI, 35.3%-52.2%; P < 0.0001) after 7.5 ± 5.4 (1-22) days after dose 2. There was no difference between dose 1 and dose 2 concerning SUVmax (3.7 ± 1.8 [1.3-11.3] and 4.5 ± 3.9 [1.4-26.3], P = 0.13, respectively), SUVmean (2.1 ± 1.0 [0.7-6.5] and 2.7 ± 2.4 [0.8-17], P = 0.08, respectively), and reactogenicity volume (2.7 ± 2.3 [0.2-11.6] cm3 and 2.7 ± 2.4 [0.2-15.5] cm3, P = 0.98, respectively). There was no difference in number and in size of positive lymph nodes between dose 1 and dose 2: 3.2 ± 2.2 (1-10) and 3.7 ± 2.4 (1-12) (P = 0.18), and 1.4 ± 0.4 cm (0.7-2.5 cm) and 1.5 ± 0.4 cm (0.6-3.2 cm) (P = 0.75), respectively. CONCLUSIONS: A cluster pattern of hypermetabolic ipsilateral small axillary lymph nodes is common after mRNA COVID-19 vaccination, mainly after the second injection.

Investigating the impact of measurement uncertainty in the radiographic surveillance of hip displacement in cerebral palsy: A Monte Carlo simulation.

Hip surveillance programmes have greatly improved the management of hip dysplasia in children with cerebral palsy. Reimer's migration percentage is the most common index for quantifying hip dysplasia from planar radiographs. However, measurement uncertainty could undermine the diagnostic accuracy. A Monte Carlo simulation was created to investigate the impact of measurement error on decision making in hip surveillance programmes. The simulation was designed to mimic the annual surveillance of children with cerebral palsy (Gross Motor Functional Classification System levels III-V) between 2 and 8 years of age. Simulation parameters for the natural history of hip dysplasia and measurement error were derived from published data. At each measurement interval, the influence of uncertainty in the measurement of Reimer's migration percentage on decision-making was investigated. The probability of a child being indicated for intervention in error during the course of the simulation was relatively high, particularly in the highest functioning cohort where the positive predictive value of Reimer's migration percentage was at best 70% and at worse less than 20%. Including a rate of progression term within the decision-making algorithm had a negative effect on positive predictive power. This simulation suggests that hip surveillance programmes are sensitive to detecting genuine hip dysplasia but can have poor positive predictive power, potentially resulting in unnecessary indication for intervention.

Can clinical gait analysis guide the management of ambulant children with bilateral spastic cerebral palsy?

BACKGROUND: The role of clinical gait analysis in the management of ambulant children with bilateral spastic cerebral palsy (BSCP) is controversial. We hypothesized that gait analysis would allow us to differentiate between children with BSCP who would benefit from surgical intervention and those in whom surgery was not indicated. METHODS: We reviewed the outcome in 3 groups of children with BSCP referred for treatment recommendations based on gait analysis by looking at changes in the popliteal angle (PA), Gillette Gait Index (GGI), and minimum knee flexion in single support (MKFS) on a subsequent gait analysis. We identified 15 children in whom surgical intervention was not thought to be needed (SNR group) and 15 children who had multilevel surgery recommended but not performed (SND group). We randomly selected and reviewed 15 children referred during the study period who had multilevel surgery recommended and performed following gait analysis (OP group) for comparison. RESULTS: The initial PA, MKFS, and GGI were greater in the OP and SND groups compared with the SNR group. Popliteal angle did not change between analyses in the SNR and SND groups and decreased in the OP group (P = 0.004). Minimum knee flexion in single support remained similar between analyses in the SNR group, increased in the SND group (P < 0.0001), and decreased in the OP group (P < 0.0001). The GGI remained similar in the SNR and SND groups but decreased in the OP group (P = 0.0002). The number of children in the SND group showing an increase of more than 10% in the GGI between analyses (8/15) was greater than that in the OP group (0/15) (P = 0.0022). The PA, MKFS, and GGI contributed significantly to the treatment recommendations (P = 0.0013, P = 0.0045, P = 0.0054, respectively), which were not affected by age and Gross Motor Functional Classification System level. CONCLUSIONS: Gait analysis helped us to distinguish children with BSCP who would benefit from surgery from those in whom nonoperative management was appropriate, and its routine clinical use is encouraged in the management of these children. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Determination of the temperature rise within UHMWPE tibial components during tribological loading.

The wear of ultrahigh molecular weight polyethylene (UHMWPE) is considered as one of the major reasons for revision of artificial joints. While in vivo measurements have shown a significant temperature increase in knee implants, the amount of heat dissipated within the UHMWPE tibial component and its influence on the friction behavior when paired with a cobalt-chromium (CoCrMo) femoral component is unknown. Our goal was to address these questions by measuring the temperature rise over a wide range of tribological loading conditions that mimic certain spots on artificial knee joints. The temperature rise as a function of lubricant, sliding velocity, coefficient of friction and maximum load was determined and analyzed. Additionally, the heat gradient during constant loading was investigated that allows the calculation of heat flow. The test setup consists of a wheel-on-flat laboratory testing device. Tests were performed in ambient air and different lubricants. During the tests, the temperature rise in the polyethylene was recorded with embedded thermocouples. The temperature rise was high and shown to be directly linked to load, coefficient of friction and relative velocity. Because it is generally assumed that the applied energy is an indicator for the development of wear in particles, some considerations for the design of knee joints are proposed based on our observations. The amount of heat dissipated in the polyethylene under cyclic loading was measured and is discussed in comparison with the theoretical model of temperature in friction pairs.