Category: Statistics

Fam Med Community Health. 2021 Dec;9(Suppl 1):e001290. doi: 10.1136/fmch-2021-001290.

ABSTRACT

Family medicine has traditionally prioritised patient care over research. However, recent recommendations to strengthen family medicine include calls to focus more on research including improving research methods used in the field. Binary logistic regression is one method frequently used in family medicine research to classify, explain or predict the values of some characteristic, behaviour or outcome. The binary logistic regression model relies on assumptions including independent observations, no perfect multicollinearity and linearity. The model produces ORs, which suggest increased, decreased or no change in odds of being in one category of the outcome with an increase in the value of the predictor. Model significance quantifies whether the model is better than the baseline value (ie, the percentage of people with the outcome) at explaining or predicting whether the observed cases in the data set have the outcome. One model fit measure is the count- [Formula: see text], which is the percentage of observations where the model correctly predicted the outcome variable value. Related to the count- [Formula: see text] are model sensitivity-the percentage of those with the outcome who were correctly predicted to have the outcome-and specificity-the percentage of those without the outcome who were correctly predicted to not have the outcome. Complete model reporting for binary logistic regression includes descriptive statistics, a statement on whether assumptions were checked and met, ORs and CIs for each predictor, overall model significance and overall model fit.

PMID:34952854 | DOI:10.1136/fmch-2021-001290

Indian J Dermatol Venereol Leprol. 2021 Oct 20:1-4. doi: 10.25259/IJDVL_917_19. Online ahead of print.

ABSTRACT

INTRODUCTION: Neuropathic pain is a common and disabling late complication of leprosy. We investigated the clinical and electrophysiological characteristics of neuropathic pain in leprosy patients by evaluating nerve conduction, sympathetic skin response (SSR) and A-waves.

METHODS: Twenty one leprosy patients with neuropathic pain validated by the Douleur Neuropathique en 4 (DN4)Questionnaire were selected for study. Pain intensity was measured by the visual analog scale. Demographic and clinical data were collected for all patients. Clinical data included appraisal of the median, ulnar, radial, tibial and common peroneal nerves, assessment of the sympathetic skin response and conventional electrophysiological recordings.

RESULTS: Among all electroneuromyographic presentations, multifocal mononeuropathy was still the most prevalent. Sensory loss was observed more frequently than motor deficits. As most patients presented advanced clinical forms of leprosy and were under treatment, this high mean was found and the ulnar nerve was most frequently affected. The sympathetic skin response was absent in 16 patients. Higher DN4 Questionnaire scores were observed in women and in those receiving corticosteroid therapy. These inferences are possible to be made, but our study’s limitations don’t allow us to be certain about it. The statistical significance found only permits us to evidence what we related on the textual part of the study.

LIMITATIONS: The small number of patients studied, the lack of sophisticated diagnostic methods for leprosy, as well as the difficulties in assessing nerve conduction were the main limitations of this study.

CONCLUSION: The neurophysiological and clinical findings in leprous neuropathy were modest despite the conspicuous neuropathic pain. Although electrophysiological studies are a vital tool to verify nerve damage, variations in the clinical presentation of leprosy neuropathic pain render the diagnosis challenging. Further studies are needed to describe the neurophysiological evolution of this disease.

PMID:34951937 | DOI:10.25259/IJDVL_917_19

Phys Rev Lett. 2021 Dec 10;127(24):240401. doi: 10.1103/PhysRevLett.127.240401.

ABSTRACT

Self-testing is a device-independent method that usually amounts to show that the maximal quantum violation of a Bell’s inequality certifies a unique quantum state, up to some symmetries inherent to the device-independent framework. In this work, we enlarge this approach and show how a coarse-grained version of self-testing is possible in which physically relevant properties of a many-body system are certified. To this aim we study a Bell scenario consisting of an arbitrary number of parties and show that the membership to a set of (entangled) quantum states whose size grows exponentially with the number of parties can be self-tested. Specifically, we prove that a many-body generalization of the chained Bell inequality is maximally violated if and only if the underlying quantum state is equal, up to local isometries, to a many-body singlet. The maximal violation of the inequality therefore certifies any statistical mixture of the exponentially many orthogonal pure states spanning the singlet manifold.

PMID:34951817 | DOI:10.1103/PhysRevLett.127.240401

Opt Lett. 2022 Jan 1;47(1):142-145. doi: 10.1364/OL.445691.

ABSTRACT

Extreme events (EEs) are predicted for the first time, to the best of our knowledge, in the chaotic dynamics of a free-running spin-polarized vertical-cavity surface-emitting laser (spin-VCSEL). Here, we not only show two types of EEs, i.e., vectorial and scalar EEs separately corresponding to the emission of a high-power pulse in both linear polarizations (LPs) simultaneously and in single LP, but we also observe a new EE type that only occurs in total intensity. We also confirm that the observed EEs follow similar statistical distributions to conventional rogue waves. Moreover, the effects of pump power and pump ellipticity on the generation of EEs are analyzed. Finally, we compare free-running and optical feedback spin-VCSELs, which provides more insights into the study of EEs. More importantly, this work offers a novel platform for the study of EEs with a simple structure and opens up new research fields into spin-VCSELs.

PMID:34951902 | DOI:10.1364/OL.445691

Phys Rev Lett. 2021 Dec 10;127(24):240603. doi: 10.1103/PhysRevLett.127.240603.

ABSTRACT

Identifying the relevant degrees of freedom in a complex physical system is a key stage in developing effective theories in and out of equilibrium. The celebrated renormalization group provides a framework for this, but its practical execution in unfamiliar systems is fraught with ad hoc choices, whereas machine learning approaches, though promising, lack formal interpretability. Here we present an algorithm employing state-of-the-art results in machine-learning-based estimation of information-theoretic quantities, overcoming these challenges, and use this advance to develop a new paradigm in identifying the most relevant operators describing properties of the system. We demonstrate this on an interacting model, where the emergent degrees of freedom are qualitatively different from the microscopic constituents. Our results push the boundary of formally interpretable applications of machine learning, conceptually paving the way toward automated theory building.

PMID:34951810 | DOI:10.1103/PhysRevLett.127.240603

Phys Rev Lett. 2021 Dec 10;127(24):241102. doi: 10.1103/PhysRevLett.127.241102.

ABSTRACT

High-quality optical resonant cavities require low optical loss, typically on the scale of parts per million. However, unintended micron-scale contaminants on the resonator mirrors that absorb the light circulating in the cavity can deform the surface thermoelastically and thus increase losses by scattering light out of the resonant mode. The point absorber effect is a limiting factor in some high-power cavity experiments, for example, the Advanced LIGO gravitational-wave detector. In this Letter, we present a general approach to the point absorber effect from first principles and simulate its contribution to the increased scattering. The achievable circulating power in current and future gravitational-wave detectors is calculated statistically given different point absorber configurations. Our formulation is further confirmed experimentally in comparison with the scattered power in the arm cavity of Advanced LIGO measured by in situ photodiodes. The understanding presented here provides an important tool in the global effort to design future gravitational-wave detectors that support high optical power and thus reduce quantum noise.

PMID:34951783 | DOI:10.1103/PhysRevLett.127.241102

Phys Rev Lett. 2021 Dec 10;127(24):242002. doi: 10.1103/PhysRevLett.127.242002.

ABSTRACT

We present an analysis of the pion-nucleon σ-term σ_{πN} using six ensembles with 2+1+1-flavor highly improved staggered quark action generated by the MILC Collaboration. The most serious systematic effect in lattice calculations of nucleon correlation functions is the contribution of excited states. We estimate these using chiral perturbation theory (χPT) and show that the leading contribution to the isoscalar scalar charge comes from Nπ and Nππ states. Therefore, we carry out two analyses of lattice data to remove excited-state contamination, the standard one and a new one including Nπ and Nππ states. We find that the standard analysis gives σ_{πN}=41.9(4.9) MeV, consistent with previous lattice calculations, while our preferred χPT-motivated analysis gives σ_{πN}=59.6(7.4) MeV, which is consistent with phenomenological values obtained using πN scattering data. Our data on one physical pion mass ensemble were crucial for exposing this difference, therefore, calculations on additional physical mass ensembles are needed to confirm our result and resolve the tension between lattice QCD and phenomenology.

PMID:34951792 | DOI:10.1103/PhysRevLett.127.242002

Zh Vopr Neirokhir Im N N Burdenko. 2021;85(6):68-74. doi: 10.17116/neiro20218506168.

ABSTRACT

A ridit analysis of results of transpedicular endoscopic and translaminar microsurgical surgeries for sequester migration to the second and third McCulloch’s windows was carried out. The authors assessed pain syndrome, quality of life and neurological impairment.

OBJECTIVE: To compare the outcomes of transpedicular and translaminar sequestrectomy for lumbar disc herniation and sequester migration to the second and third McCulloch’s windows.

MATERIAL AND METHODS: We analyzed treatment outcomes in 51 patients with lumbar disc herniation and severe sequester migration. We assessed lumbar and leg pain syndrome using then visual analogue scale, neurological impairment using the adapted Nurik scale and quality of life using the Oswestry questionnaire and the MacNab scale in early postoperative period, as well as in 2 weeks, 6 and 12 months after surgery. Ridit analysis was used for statistical processing of data.

RESULTS: Transpedicular sequestrectomy was performed in 24 patients, translaminar sequestrectomy – in 27 cases. Groups were comparable by gender, size and location of sequestration, somatic and neurological status, as well as pain severity. There was a higher probability of back (0.39) and leg (0.364) pain regression, neurological recovery (0.446) and improvement of quality of life according to the Oswestry questionnaire (0.389) after transpedicular surgery. According to the MacNab scoring system, excellent and good results were obtained in 84.21% and 15.79% of patients in 6 months after transpedicular surgery. In the second group, excellent, good and satisfactory results were obtained in 63%, 25.9% and 11.1% of patients, respectively.

CONCLUSION: Herniated intervertebral discs with severe sequester migration should be divided in accordance with localization of the main sequestration. Transpedicular endoscopic approach is advisable for sequester in the third and rarely the second McCulloch’s windows. Translaminar microsurgical approach is preferred for sequestration in the second and rarely the third McCulloch’s windows. Clinical outcomes after translaminar microsurgical sequestrectomy and transpedicular endoscopic surgeries are similar. However, postoperative back and leg pain regression, neurological recovery and improvement of quality of life according to the Oswestry scoring system are more common after transpedicular surgery.

PMID:34951762 | DOI:10.17116/neiro20218506168

Zh Vopr Neirokhir Im N N Burdenko. 2021;85(6):26-35. doi: 10.17116/neiro20218506126.

ABSTRACT

BACKGROUND: One of the most difficult problems in surgical treatment of moyamoya disease is prevention of ischemic perioperative complications. The risk of these events is significantly higher compared to other cerebrovascular diseases (up to 30%).

OBJECTIVE: To identify unfavorable prognostic factors of perioperative cerebral ischemic complications, to determine the group of high-risk patients and to develop the guidelines for perioperative management of these patients.

MATERIAL AND METHODS: We analyzed clinical and diagnostic data and postoperative outcomes in 80 patients with various forms of moyamoya disease. These patients underwent 134 different interventions. Staged revascularization of both hemispheres was performed in 40 patients (80 surgeries). Most patients (n = 55) underwent combined brain revascularization (79 surgeries).

RESULTS: Persistent postoperative complications (ischemic stroke) developed in 7 cases (5.3%). Transient neurological impairment was observed in 36 cases (27%). Statistical analysis revealed the following risk factors of perioperative complications: critical stenosis/occlusion of posterior cerebral artery (OR 9.704), severe perfusion deficit (OR 5.393) and previous TIA or ischemic stroke within 3 months prior to surgery (OR 6.433). If at least two of these signs are present, sensitivity of prognosis for postoperative complications is 80.7% and 88.6%, respectively.

CONCLUSION: Patients with moyamoya disease are at high risk of perioperative complications due to complex rearrangement of collateral cerebral circulation and high sensitivity of brain to local and systemic hemodynamic changes. Patients with risk factors require careful perioperative management to exclude pathogenetic factors provoking ischemia. Early surgical treatment is advisable to reduce the risk of ischemic and hemorrhagic lesions following natural course of disease and severe perioperative complications.

PMID:34951757 | DOI:10.17116/neiro20218506126

J Biophotonics. 2021 Dec 24:e202100340. doi: 10.1002/jbio.202100340. Online ahead of print.

ABSTRACT

Optical coherence tomography angiography (OCTA) can map microvascular networks and quantify blood flow velocities with high resolution by calculating intensity standard deviations of time-series signals. However, statistical calculations of the standard deviations need much processing time and reduce the analysis efficiency. In this study, we proposed three optimized OCTA algorithms incorporating rapid estimations of the intensity standard deviations, including the range algorithm, the mean absolute error algorithm, and the maximum absolute error algorithm. The abilities of the optimized algorithms to quantify the flow velocities were validated by a flow phantom. After a rat cerebral cortex was imaged, the optimized OCTA algorithms were compared with the conventional relative standard deviation algorithm in the metrics of imaging quality and processing time. The results show that the optimized algorithms incorporating rapid estimations of the intensity standard deviations have faster processing speeds with equivalent image quality. This article is protected by copyright. All rights reserved.

PMID:34951745 | DOI:10.1002/jbio.202100340