Category: Statistics

Phys Rev E. 2024 Sep;110(3-1):034126. doi: 10.1103/PhysRevE.110.034126.

ABSTRACT

We investigate how to count the number of solutions in the Boolean satisfiability (SAT) problem, a fundamental problem in theoretical computer science that has applications in various domains. We convert the problem to a spin-glass problem in statistical physics and approximately compute the entropy of the problem, which corresponds to the logarithm of the number of solutions. We propose a new method for the entropy computing problem based on a combination of the tensor network method and the message-passing algorithm. The significance of the proposed method is its ability to consider the effects of both long loops and short loops present in the factor graph of the SAT problem. We validate the efficacy of our approach using 3-SAT problems defined on the random graphs and structured graphs, and show that the proposed method gives more accurate results on the number of solutions than the standard belief propagation algorithms. We also discuss the applications of our method across a wide range of combinatorial optimization problems.

PMID:39425436 | DOI:10.1103/PhysRevE.110.034126

Phys Rev E. 2024 Sep;110(3-2):035206. doi: 10.1103/PhysRevE.110.035206.

ABSTRACT

Ablator materials used for inertial confinement fusion, such as high-density carbon (HDC) and beryllium, have grain structure which may lead to small-scale density nonuniformity and the generation of perturbations when the materials are shocked and compressed. Here, we use a combination of a linear theory of shock interaction with density nonuniformity [Velikovich et al., Phys. Plasmas 14, 072706 (2007)10.1063/1.2745809] and numerical simulations to study shock interaction with a model representation of HDC grains. While the shock-grain interaction is nonlinear, the linear theory shows some key features of the shock-grain interaction, which also hold for the (nonlinear) simulations. The postshock perturbations are made up of sonic reflections off of grain boundaries and vorticity deposition along them, with the latter dominating the perturbed energy content. The mean (per mass) postshock perturbed kinetic energy decreases with increasing grain size, but energy will be deposited at increasing spatial scale. From the perspective of the postshock perturbed energy, the detailed linear theory largely supports a proposed method [S. Davidovits et al., Phys. Plasmas 29, 112708 (2022)1070-664X10.1063/5.0107534] for deresolving the grains (in a similar grains model) that treats the grains statistically. Our simulation results highlight the influence of thermal conduction on the perturbation dynamics at grain scales.

PMID:39425435 | DOI:10.1103/PhysRevE.110.035206

Phys Rev E. 2024 Sep;110(3-1):034305. doi: 10.1103/PhysRevE.110.034305.

ABSTRACT

Random network models, constrained to reproduce specific statistical features, are often used to represent and analyze network data and their mathematical descriptions. Chief among them, the configuration model constrains random networks by their degree distribution and is foundational to many areas of network science. However, configuration models and their variants are often selected based on intuition or mathematical and computational simplicity rather than on statistical evidence. To evaluate the quality of a network representation, we need to consider both the amount of information required to specify a random network model and the probability of recovering the original data when using the model as a generative process. To this end, we calculate the approximate size of network ensembles generated by the popular configuration model and its generalizations, including versions accounting for degree correlations and centrality layers. We then apply the minimum description length principle as a model selection criterion over the resulting nested family of configuration models. Using a dataset of over 100 networks from various domains, we find that the classic configuration model is generally preferred on networks with an average degree above 10, while a layered configuration model constrained by a centrality metric offers the most compact representation of the majority of sparse networks.

PMID:39425431 | DOI:10.1103/PhysRevE.110.034305

Phys Rev E. 2024 Sep;110(3-2):035301. doi: 10.1103/PhysRevE.110.035301.

ABSTRACT

In this paper we first propose a phase-field model for the containerless freezing problems, in which the volume expansion or shrinkage of the liquid caused by the density change during the phase change process is considered by adding a mass source term to the continuum equation. Then a phase-field-based lattice Boltzmann (LB) method is further developed to simulate solid-liquid phase change phenomena in multiphase systems. We test the developed LB method by the problem of conduction-induced freezing in a semi-infinite space, the three-phase Stefan problem, and the droplet solidification on a cold surface, and the numerical results are in agreement with the analytical and experimental solutions. In addition, the LB method is also used to study the rising bubbles with solidification. The results of the present method not only accurately capture the effect of bubbles on the solidification process, but also are in agreement with the previous work. Finally, a parametric study is carried out to examine the influences of some physical parameters on the sessile droplet solidification, and it is found that the time of droplet solidification increases with the increase of droplet volume and contact angle.

PMID:39425430 | DOI:10.1103/PhysRevE.110.035301

J Psychosom Res. 2024 Oct 11;187:111954. doi: 10.1016/j.jpsychores.2024.111954. Online ahead of print.

ABSTRACT

BACKGROUND: The response to cognitive behavioral therapy (CBT) for chronic fatigue syndrome (CFS) varies greatly between patients, but predictors of treatment success remain to be elucidated. We aimed to identify patient subgroups based on fatigue trajectory during CBT, identify pre-treatment predictors of subgroup membership, and disentangle the direction of predictor – outcome relationships over time.

METHODS: 297 individuals with CFS were enrolled in a standardized CBT program consisting of 17 sessions, with session timing variable between participants. Self-reported levels of fatigue, depressive, anxiety, and somatic symptoms, perceived stress, and positive affect were collected pre-treatment, and after 3, 10, and 15 sessions. Latent Class Growth Analysis (LCGA) was used to identify subgroups based on fatigue trajectories and baseline predictors of group membership. Cross-lagged structural equation models were used to disentangle predictor-outcome relationships.

RESULTS: LCGA identified four fatigue trajectory subgroups, which were labelled as “no improvement” (23 %), “weak improvement” (45 %), “moderate improvement” (23 %), and “strong improvement” (9 %) classes. Higher pre-treatment levels of depressive, anxiety, and somatic symptoms, stress, and lower levels of positive affect predicted membership of the “no improvement” subgroup. Reductions in anxiety preceded reductions in fatigue, while the depressive symptoms – fatigue relationship was bidirectional.

CONCLUSIONS: On a group level, there were statistically significant reductions in fatigue after 15 sessions of CBT, with important individual differences in treatment response. Higher pre-treatment levels of anxious, depressive, and somatic symptoms and perceived stress are predictors of lack of response, with reductions in anxiety and stress preceding improvements in fatigue.

PMID:39423465 | DOI:10.1016/j.jpsychores.2024.111954

Vaccine. 2024 Oct 17;42(26):126442. doi: 10.1016/j.vaccine.2024.126442. Online ahead of print.

ABSTRACT

INTRODUCTION: In 2014, South Africa implemented a national two-dose HPV vaccination programme using the bivalent vaccine for girls aged 9 years and older attending Grade 4 at public schools. We assessed HPV prevalence and risk factors among South African adolescent girls and young women (AGYW) aged 17-18 years who were ineligible for vaccination.

METHODS: From June to December 2019, we surveyed AGYW aged 17-18 years attending primary care clinics in four South African provinces. Consenting participants completed a questionnaire, underwent HIV counselling and testing, and self-collected a vaginal swab for HPV testing. Samples were tested by Seegene AnyPlex™ II HPV28. We used summary statistics to describe the population characteristics and logistic regression to examine the association between risk factors and high-risk HPV detection.

RESULTS: 910 participants were screened, 900 enrolled, 896 had valid HPV results, and 819 were unvaccinated and included in this study. Of these, 248 (30.3 %) were living with HIV and 597 (72.9 %) reported ever having vaginal sex. Overall, 463 (56.5 %) had at least one high-risk HPV detected, and 177 (21.6 %) had HPV16/18 detected. AGYW living with HIV had a higher prevalence of any high-risk HPV (65.3 % vs 52.7 %, p < 0.001) and HPV 16/18 (29.4 % vs 18.2 %, p < 0.001) compared to those without HIV. Multiple infections were also more common in participants living with HIV, with three or more high-risk HPV types detected in 32.3 % compared with 15.4 % of those without HIV (p < 0.001). In multivariate analyses, HIV status (p < 0.001) and higher number of lifetime sexual partners (p-trend<0.001) were associated with high-risk HPV detection.

CONCLUSIONS: High-risk HPV was very common in unvaccinated South Africa AGYW, especially among those living with HIV, highlighting the importance of HPV vaccination in settings with high HIV prevalence.

PMID:39423451 | DOI:10.1016/j.vaccine.2024.126442

J Neurosurg Spine. 2024 Oct 18:1-10. doi: 10.3171/2024.7.SPINE24206. Online ahead of print.

ABSTRACT

OBJECTIVE: The goal of this study was to evaluate the comparative outcomes of aggressive debulking (AD) and minimal decompression (MD) surgeries for metastatic spinal cord compression based on surgical burden, functional improvement, and symptomatic local recurrence (SLR).

METHODS: In this retrospective analysis from 2 tertiary hospitals, the authors assessed patients with metastatic spinal cord compression treated via AD and MD surgeries between 2010 and 2022. The evaluation included patient demographics, Eastern Cooperative Oncology Group performance status (ECOG-PS), primary tumor type, modified Tokuhashi scores, surgical burden, and SLR. Propensity-score matching (1:1 ratio) was conducted based on oncological status for intergroup comparisons. Survival analysis and logistic regression analyses were conducted.

RESULTS: A total of 264 patients were included in the study. After 1:1 propensity-score matching, a total of 156 matched patients were analyzed (78 patients each in the AD and MD groups). Operation time, estimated blood loss, transfused red blood cell units, and inpatient medical complications were significantly higher in the AD group compared to the MD group (p = 0.001, p = 0.002, p = 0.006, and p = 0.035, respectively). There was no significant difference in distribution of postoperative ECOG-PS between the AD and MD groups (OR 1.461, 95% CI 0.821-2.599, p = 0.197). In initially nonambulatory patients (ECOG-PS of grade 3 or 4), the AD group showed a higher proportion of patients regaining ambulatory function compared to the MD group (56.5% vs 36.2%; OR 2.294, p = 0.049). In cases with a preoperative ECOG-PS of grade 3, the difference in ambulation recovery between AD and MD was not statistically significant (60.0% vs 53.3%, p = 0.577). However, for severely impaired patients (ECOG-PS of grade 4), the AD group showed a higher proportion of patients regaining ambulatory function compared to the MD group (33.3% vs 5.9%, p = 0.086). Symptomatic SLR-free survival showed no significant differences at final follow-up (p = 0.095). Multivariate analysis identified the modified Tokuhashi score as the sole predictor of SLR (OR 1.871, p = 0.001).

CONCLUSIONS: This study found that MD surgery significantly reduced surgical burden compared to AD. AD surgery led to slightly better functional recovery showing greater rescue ratios, especially in patients with a preoperative ECOG-PS of grade 4. However, no difference in rescue ratio was observed in patients with a preoperative ECOG-PS of grade 3. There was no significant difference in SLR rates between the AD and MD groups.

PMID:39423444 | DOI:10.3171/2024.7.SPINE24206

J Neurosurg. 2024 Oct 18:1-9. doi: 10.3171/2024.6.JNS24597. Online ahead of print.

ABSTRACT

OBJECTIVE: Epilepsy is commonly associated with low-grade gliomas (LGGs), impacting patients’ well-being. While resection is the primary treatment, seizures can persist postoperatively in 27%-55% of cases. The authors aimed to evaluate an electrocorticography (ECoG) and navigated transcranial magnetic stimulation (nTMS)-tailored supratotal resection (ETT-SpTR) for LGG in controlling seizures, preserving neurological function, and enhancing treatment effectiveness.

METHODS: The authors retrospectively analyzed a prospectively enrolled cohort of patients with LGG presenting with epileptic seizures with ictal/interictal activity on electroencephalography (EEG) who underwent resective surgery. The authors performed preoperative nTMS to identify functional cortical areas. ECoG was used to guide the removal of the high-risk epilepsy cortical areas (HREAs). Patients were divided into two groups: group I, the control group, underwent gross-total resection alone, whereas group II patients underwent removal of HREAs identified by ECoG (ETT-SpTR). Resection avoided functionally eloquent areas as identified on nTMS, checked with cortical mapping. Postoperative seizure outcome was assessed using the Engel classification.

RESULTS: Fifteen patients who underwent LGG resection between January and July 2023 were included. Among 24 identified nTMS-positive points, none were included in the resection. Overall, 73.3% of patients (11/15) showed positive intraoperative ECoG, with better outcomes in group II (85.7% Engel class IA) than in group I (25% Engel class IA) at the follow-up (p = 0.02, OR 0.5 [95% CI 0.035-7.10], RR 0.19 [95% CI 0.03-1.2]). Seizure control was significantly better in group II, with no notable differences in postoperative transient neurological deficits between the two groups (p = 0.45). No permanent neurological deficits were observed during follow-up. Statistical analysis revealed significant differences between the two groups (p < 0.05).

CONCLUSIONS: This preliminary study affirms the predictive value of TMS for postoperative neurological status and safety in epileptic patients. Intraoperative ECoG effectively identified peritumoral HREAs. ETT-SpTR significantly improved epileptic outcomes, preserving functions without permanent neurological worsening. Additional resection targets the HREAs in the temporal, frontal, and parietal lobes.

PMID:39423425 | DOI:10.3171/2024.6.JNS24597

J Neurosurg Pediatr. 2024 Oct 18:1-7. doi: 10.3171/2024.7.PEDS24237. Online ahead of print.

ABSTRACT

OBJECTIVE: Pediatric neurosurgical practice is prevalent in most low- and lower-middle-income countries but lacks comprehensive documentation of practice patterns, demographics, and case variety. This study aimed to present the current state of pediatric neurosurgery in Ethiopia, including workforce characterization, case variety, and relevant procedures.

METHODS: A survey was developed and distributed to all Ethiopian fully trained neurosurgeons (n = 50). Survey questions assessed sociodemographic variables, level of training, case variety, and neurosurgical practice. Statistical analysis was conducted to describe the current practice of pediatric neurosurgery.

RESULTS: A total of 45 neurosurgeons responded (90%). Three respondents (7%) were women. There was only 1 fellowship-trained pediatric neurosurgeon, while most neurosurgeons were general neurosurgeons who served a pediatric patient population. Most neurosurgeons (56%) worked in the capital city, Addis Ababa, while another 13% worked in other urban settings. The top three indications for a pediatric neurosurgical procedure were neural tube defects (NTDs) (96%), hydrocephalus (93%), and trauma (60%). NTD-associated hydrocephalus was the most common hydrocephalus type seen (71%). The most common procedure for hydrocephalus was shunt insertion (96%). A prenatal diagnosis of NTD was made in < 10% of cases, as reported by 84% of respondents.

CONCLUSIONS: The study highlights Ethiopia’s need for more pediatric neurosurgeons. Suggested strategies to facilitate subspecialty training include the establishment of a fellowship program facilitated by the implementation of a nationwide pediatric neurosurgery registry. Promoting efforts for early diagnosis and treatment of pediatric conditions coupled with NTD prevention initiatives could improve pediatric neurosurgical care in Ethiopia.

PMID:39423423 | DOI:10.3171/2024.7.PEDS24237