Number Of Conditions Research Articles

A mid‑pandemic night's dream: Melatonin, fromharbinger of anti‑inflammation to mitochondrial savior in acute and long COVID‑19 (Review).

Coronavirus disease 2019 (COVID‑19), a systemic illness caused by severe acute respiratory distress syndrome2 (SARS‑CoV‑2), has triggered a worldwide pandemic with symptoms ranging from asymptomatic to chronic, affecting practically every organ. Melatonin, an ancient antioxidant found in all living organisms, has been suggested as a safe and effective therapeutic option for the treatment of SARS‑CoV‑2 infection due to its good safety characteristics and broad‑spectrum antiviral medication properties. Melatonin is essential in various metabolic pathways and governs physiological processes, such as the sleep‑wake cycle and circadian rhythms. It exhibits oncostatic, anti‑inflammatory, antioxidant and anti‑aging properties, exhibiting promise for use in the treatment of numerous disorders, including COVID‑19. The preventive and therapeutic effects of melatonin have been widely explored in a number of conditions and have been well‑established in experimental ischemia/reperfusion investigations, particularly in coronary heart disease and stroke. Clinical research evaluating the use of melatonin in COVID‑19 has shown various improved outcomes, including reduced hospitalization durations; however, the trials are small. Melatonin can alleviate mitochondrial dysfunction in COVID‑19, improve immune cell function and provide antioxidant properties. However, its therapeutic potential remains underexplored due to funding limitations and thus further investigations are required.

Association between serum lactate, lactate clearance rate, and 30-day mortality among patients undergoing mechanical ventilation: A retrospective cohort study of MIMIC-III database.

Serum lactate has been used as a prognostic indicator in intensive care unit patients, and however, the single lactate value may not be enough to reflect changes during illness conditions. Herein, this study aims to explore the association between serum lactate and lactate clearance rate and 30-day mortality in patients undergoing mechanical ventilation (MV). Demographic and clinical data of 2628 adults were extracted from the medical information mart for intensive care-III clinical database in this retrospective cohort study. The lactate clearance rate was calculated using the serum lactate at the beginning of MV (T0), and serum lactate at the12 hours after MV beginning (T1). Univariate and multivariate Cox regression analyses were used to screen covariates, and explore the association between serum lactate and lactate clearance rate and 30-day mortality. We also explored these associations in different T0 serum lactate level subgroups. The evaluation indexes were hazard ratios (HRs) and 95% CIs. In addition, receiver operator characteristic (ROC) curve with area under the curve (AUC) was used to reflect the predictive performance of serum lactate and lactate clearance rate on 30-day mortality. A total of 827 (31.47%) mechanically ventilated patients died within 30 days. After adjusting for covariates, elevated T0 (HR = 1.04, 95%CI: [1.02-1.07]) and T1 (HR = 1.07, 95%CI: [1.04-1.10]) serum lactate was both associated with an increased risk of 30-day mortality, while higher lactate clearance rate was negatively associated with the risk of 30-day mortality (HR = 0.64, 95%CI: [0.50-0.81]). Among patients with T0 lactate ≥2 mmol/L, T1 serum lactate ≥4 mmol/L was associated with an increased risk of 30-day mortality, while lactate clearance rate ≥50 was associated with a decreased risk (all P < .05). Moreover, T1 serum lactate had a potential predictive value on 30-day mortality with an AUC of 0.605. Serum lactate and lactate clearance rate were both associated with 30-day mortality in patients undergoing MV. Our results may provide some references for further studies to explore the roles of serum lactate and lactate clearance rate in prognoses of critical patients.

RSSI Measurement Analysis of Zigbee-Based Wireless Sensor Networks in Various Topologies for Solar Panel Monitoring

Abstract— Solar panels require performance monitoring when energy shortages occur in the area. Monitoring solar panels requires a detection device to detect solar panels, including the ACS712 current sensor for monitoring the output current of the solar panel, a DC voltage sensor for monitoring battery performance, and a DHT11 temperature sensor for monitoring the temperature of the solar panel storage battery. The WSN technology that can work is ZigBee communication. This ZigBee communication research uses various topology methods, including star, tree, and mesh topologies. Solar panel monitoring tests are carried out indoors and outdoors. The ZigBee communication device used is the XBee S2C device, which operates at a frequency of 2.4 GHz. From a comparison of various topologies, the mesh topology is a topology with good performance because it has the characteristic of choosing a router with the fastest path to reach the coordinator. It is proven by monitoring solar panels with an optimal distance of 80 m, which is carried out from outdoors with an RSSI value of -84 dBm, a throughput of 0.55 kbps, and a delay of 2.77 ms, producing power for 150 minutes with an average current of 0.14 A, voltage of 9.86 V, and temperature of 31.48°C. The number of disturbances and weather conditions greatly affect signal propagation, which can hamper the data transmission process. Throughput fluctuates due to uncertain weather conditions, and delay fluctuates due to a lot of interference from other radio signals.&#x0D; Keyworrds— Wireless Sensor Nirbael (WSN), RSSI, ZigBee, Panel Surya, Thinger.IO

Differences in provider recommendations for Black/African American and White patients with irritable bowel syndrome.

Health disparities and barriers to equitable care for patients from racial and ethnic minority backgrounds are common. We sought to evaluate disparities in management recommendations among Black/African American (AA) patients seeking care for IBS. We assembled a retrospective cohort of patients at two tertiary care centers who were self-identifying as Black/AA and attended a first gastroenterology consult for IBS. These patients were age- and sex-matched to White controls with IBS also attending an initial gastroenterology consult. Retrospective chart review determined patient demographics, income, comorbidities, as well as provider management recommendations including pharmacologic therapies and non-pharmacologic interventions. Among 602 IBS patients ages 14-88 (M ± SD = 43.6 ± 18.6 years) with IBS, those who identified as Black/AA (n = 301) had a lower estimated mean income and were significantly more likely to have a number of specific chronic medical conditions. Black/AA patients were significantly less likely to have implemented dietary changes for symptoms prior to receiving a diagnosis of IBS from a gastroenterologist. Black/AA patients were also less likely to receive a referral to a dietician within 1 year following their diagnosis of IBS (p = 0.01). Black/AA patients were prescribed pharmacologic therapy more often for constipation (41.9% vs. 34.6%, p = 0.01). It was more common for White patients to present at the initial encounter having already initiated a neuromodulator (41.9% vs. 27.9%, p < 0.001). Management recommendations for IBS appear to vary by race, specifically for dietary advice and referrals.

Health Care Contact Days Among Older Adults in Traditional Medicare : A Cross-Sectional Study.

Days spent obtaining health care outside the home can represent not only access to needed care but also substantial time, effort, and cost, especially for older adults and their care partners. Yet, these "health care contact days" have not been characterized. To assess composition of, variation and patterns in, and factors associated with contact days among older adults. Cross-sectional study. Nationally representative 2019 Medicare Current Beneficiary Survey data linked to claims. Community-dwelling adults aged 65 years and older in traditional Medicare. Ambulatory contact days (days with a primary care or specialty care office visit, test, imaging, procedure, or treatment) and total contact days (ambulatory days plus institutional days in a hospital, emergency department, skilled-nursing facility, or hospice facility); multivariable mixed-effects Poisson regression to identify patient factors associated with contact days. In weighted results, 6619 older adults (weighted: 29 694 084) had means of 17.3 ambulatory contact days (SD, 22.1) and 20.7 total contact days (SD, 27.5) in the year; 11.1% had 50 or more total contact days. Older adults spent most contact days on ambulatory care, including primary care visits (mean [SD], 3.5 [5.0]), specialty care visits (5.7 [9.6]), tests (5.3 [7.2]), imaging (2.6 [3.9]), procedures (2.5 [6.4]), and treatments (5.7 [13.3]). Half of the test and imaging days were not on the same days as office visits (48.6% and 50.1%, respectively). Factors associated with more ambulatory contact days included younger age, female sex, White race, non-Hispanic ethnicity, higher income, higher educational attainment, urban residence, more chronic conditions, and care-seeking behaviors (for example, "go to the doctor…as soon as (I)…feel bad"). Study population limited to those in traditional Medicare. On average, older adults spent 3 weeks in the year getting care outside the home. These contact days were mostly ambulatory and varied widely not only by number of chronic conditions but also by sociodemographic factors, geography, and care-seeking behaviors. These results show factors beyond clinical need that may drive overuse and underuse of contact days and opportunities to optimize this person-centered measure to reduce patient burdens, for example, via care coordination. National Institute on Aging.

Epidemiology of multimorbidity associated with atherosclerotic cardiovascular disease in the United States, 1999–2018

BackgroundThe multimorbidity of Atherosclerotic cardiovascular disease (ASCVD) and many other chronic conditions is becoming common. This study aimed to assess multimorbidity distribution in ASCVD among adults in the United States from 1999 to 2018.MethodsThis cross-sectional survey from the National Health and Nutrition Examination Survey (NHANES) 1999–2018 using stratified multistage probability design. Among the 53,083 survey respondents during the study period, 5,729 US adults aged ≥ 20 years with ASCVD. Joinpoint regression was used to assess the statistical significance of prevalence trends in the prevalence of ASCVD stratified by multimorbidity. The Apriori association rule mining algorithm was used to identify common multimorbidity association patterns in ASCVD patients.ResultsOverall, 5,729 of 53,083 individuals had ASCVD, and the prevalence showed a slow declining trend (biannual percentage change = -0.81%, p = 0.035, average 7.71%). The prevalence of ASCVD significantly decreased in populations without dyslipidemia, diabetes mellitus (DM), hypertension, asthma, chronic obstructive pulmonary disease (COPD), and arthritis (all groups, p < 0.05). Additionally, 65.6% of ASCVD patients had at least four of the 12 selected chronic conditions, with four and five being the most common numbers of conditions (17.9% and 17.7%, respectively). The five most common chronic conditions were (in order) dyslipidemia, hypertension, arthritis, chronic kidney disease, and DM. The coexistence of hypertension and dyslipidemia had the highest support in association rules (support = 0.63), while the coexistence of dyslipidemia, hypertension, metabolic syndrome, and DM had the highest lift (lift = 1.82).ConclusionsDuring the 20-year survey period, there was a significant decrease in the overall prevalence of ASCVD. However, this reduction was primarily observed in individuals without dyslipidemia, DM, hypertension, asthma, COPD, and arthritis. Among populations with any of the evaluated chronic conditions, the prevalence of ASCVD remained unchanged. Most of ASCVD patients had four or more concurrent chronic conditions.

2012 The long-term clinical outcomes of older adults with frailty following acute hospital admission in Tanzania

Abstract Background Non-communicable disease, multimorbidity and frailty are posing considerable challenges as global populations age. Healthcare systems in Low- and Middle-Income Countries are having to rapidly adapt services to meet the needs of older people. Objective This study, the first of its kind in sub-Saharan Africa, aimed to establish whether screening older people for frailty on admission to hospital could be used to identify those at greatest risk of adverse outcomes. Methods At baseline assessment, 308 participants aged ≥60 years, admitted to medical wards at four hospitals in the Kilimanjaro Region of Tanzania, were screened for frailty using the Clinical Frailty Scale (CFS). After 10-12 months, participants, and their informants, were contacted by telephone to establish clinical outcomes. The primary outcome was all-cause mortality. Cox regression was used to estimate hazard ratios ( 95% confidence interval) for mortality, with dichotomised CFS frailty status (frail if ≥5) as the independent variable. Results Primary outcome data were obtained for 194 (63.0%) of the original participants after a mean follow-up period of 10.8 ( 0.9) months. Mean age was 75.1 years and 99 (51%) of respondents were female. A total of 100 (51.5%) respondents were deceased and hazard ratios for all-cause mortality demonstrate that those with frailty were at significantly greater risk of mortality (HR 2.27 [CI 1.39 – 3.69], p&amp;lt;0.01), an effect that persisted even after adjustment for age, baseline Barthel Index, education and number of chronic conditions. Conclusion For older people living in Tanzania, unplanned admission to hospital is associated with high mortality and frailty is a strong independent predicator. In accurately identifying which older people are at the greatest risk, frailty screening using the CFS could provide a starting point for the development of targeted care pathways and interventions.

Comparative Gas chromatography-mass spectrometry (GC-MS) analysis of two cultivars of Hordeum vulgare L.

Hordeum vulgare L. is a multi-nutritional food grain crop of the Poaceae family. It is a significant staple crop in Asia with significant nutritional and commercial importance. It is possible to grow this plant under a number of abiotic conditions of stress, such as fluoride stress. The objective of the current study was to determine whether two chosen cultivars of Hordeum vulgare could endure or tolerate fluoride stress conditions by using gas chromatography-mass spectrometry (GC-MS) analysis. The two H. vulgare cultivars’ seeds that were chosen, RD2786 and RD2794, were planted in pH-5 soil and allowed to mature for a month in clay pots. Different concentrations of fluoride (0, 5, 10, 15, 20 ppm) were added to the soil as supplements. Moreover, GC-MS was used to assess factors such as protein content and nitric oxide. Additional TLC analysis was carried out using a TLC sheet. As a result of free radical production, the cultivar RD2786 had higher total protein and nitric oxide scavenging enzyme (NOSA) activity than RD2794. Because of its osmoprotectant properties and ability to tolerate fluoride stress conditions, cultivar RD2786 of H. vulgare is therefore advised for farmers in fluoride-affected regions based on the results of this study.

Periodontitis and Alzheimer’s Disease: Is There a Connection?

The oral health/systemic health connection has been an area of research interest that increased dramatically during the 1990s. Periodontal disease has been associated with a number of systemic conditions, including cardiovascular disease, diabetes, pre-term low-birth-weight infants, respiratory conditions, rheumatoid arthritis, cancer, and Alzheimer’s disease. Inflammation is the obvious link that connects periodontal disease with these conditions, but is this association casual or causal? We will address the biologic plausibility, evidence from human studies, evidence from animal studies, and therapeutic interventions as we review the current understanding of the link between periodontitis and Alzheimer’s disease.

Recent Advances in the Diagnosis, Pathogenesis, and Management of Myxoinflammatory Fibroblastic Sarcoma.

Myxoinflammatory fibroblastic sarcoma (MIFS) is an infiltrative, locally aggressive fibroblastic neoplasm of intermediate malignancy that typically arises in the distal extremities of middle-aged adults. It can histologically be confused with a number of benign and malignant conditions. Recently, high-grade examples of MIFS have been described. Immunohistochemistry plays a very limited role in the diagnosis of MIFS. Several genetic alterations have been identified in MIFS, including a t(1;10)(p22;q24) translocation with TGFBR3 and/or OGA rearrangements, BRAF rearrangement, and VGLL3 amplification. Although it appears that VGLL3 amplification is the most consistent alteration, the molecular pathogenesis of MIFS remains poorly understood. A wide resection is considered the standard treatment for MIFS. Radiotherapy may be a viable option in cases with inadequate surgical margins or cases where surgery is likely to cause significant functional impairment. The systemic treatment options for advanced or metastatic disease are very limited. This review provides an updated overview of the clinicoradiological features, pathogenesis, histopathology, and treatment of MIFS.

An efficient algorithm for the minimal least squares solution of linear systems with indefinite symmetric matrices

In this work, a new algorithm for solving symmetric indefinite systems of linear equations is presented. It factorizes the matrix into the form LDLt using Jacobi rotations in order to increase the pivot´s absolute value. Furthermore, Rook´s pivoting strategy is also adapted and implemented. In determinate compatible systems, the computational cost of the algorithm was similar to the cost of the Bunch-Kaufman method, but the error was approximately 50 % smaller for intermediate and large matrices, regardless of the condition number of the coefficient matrix. Furthermore, unlike Bunch-Kaufman, the new algorithm calculates with little additional cost the fundamental basis of the null space, and obtains the minimal least squares and minimum norm solutions. In minimal least squares with minimum norm problems, the new algorithm was compared with the LAPACK Complete Orthogonal Decomposition algorithm, among others. The obtained error with both algorithms was similar but the computational cost was at least 20 % smaller with the new algorithm, even though the Complete Orthogonal Decomposition is implemented in a blocked form.

Impact of cardiovascular disease on health-related quality of life among older adults in eastern China: evidence from a national cross-sectional survey.

This study explores the health-related quality of life (HRQoL) scores of Chinese older adults with Cardiovascular Disease(CVD) using the EQ-5D-3L, the aim of this study is to investigate the association between health and HRQoL in older adults with CVD. The data for this study were obtained from a cross-sectional study involving older adults residing in Chinese communities The EQ-5D-3L is used to measure the HRQoL scores in the older adults with CVD. One-way analyses were conducted using the Wilcoxon rank sum test and the Kruskal-Wallis H test to assess differences between groups. A binary logistic regression model was employed to analyze the influence each variable has on the presence of "any problem" on each dimension of EQ-5D-3L in older adults with CVD. An ordinal least squares (OLS) model is used to assess the relationship between older adults with CVD and HRQoL. The mean EQ-5D-3L score for older adults with CVD is 0.774. 40.0% of older adults with CVD reported problems with pain/discomfort, followed by Mobility (35.9%), Self-care (31.5%), and Anxiety/depression (17.0%). Binary logistic regression models show that financial resources were the main factor influencing the five dimensions of EQ-5D-3L. The OLS model further indicates that younger age, financial resources, and a lower number of chronic conditions among older adults with CVD are associated with higher HRQoL scores. Chinese older adults with CVD have low HRQoL scores. Variousfactors influence both overall HRQoL scores and scores on each EQ-5D-3L dimension. This study is helpful in enhancing society's attention to the HRQoL of older adults with CVD and taking targeted measures to improve them.

Harnessing the Systemic Biology of Functional Decline and Cachexia to Inform more Holistic Therapies for Incurable Cancers.

Options for treatment of incurable cancer remain scarce and are largely focused on limited therapeutic mechanisms. A new approach specific to advanced cancers is needed to identify new and effective treatments. Morbidity in advanced cancer is driven by functional decline and a number of systemic conditions, including cachexia and fatigue. This review will focus on these clinical concepts, describe our current understanding of their underlying biology, and then propose how future therapeutic strategies, including pharmaceuticals, exercise, and rehabilitation, could target these mechanisms as an alternative route to addressing incurable cancer.

Structured level-2 condition numbers of matrix functions

Matrix functions play an increasingly important role in many areas of scientific computing and engineering disciplines. In such real-world applications, algorithms working in floating-point arithmetic are used for computing matrix functions and additionally input data might be unreliable, e.g., due to measurement errors. Therefore, it is crucial to understand the sensitivity of matrix functions to perturbations, which is measured by condition numbers. However, the condition number itself might not be computed exactly as well due to round-off and errors in the input. The sensitivity of the condition number is measured by the so-called level-2 condition number. For the usual (level-1) condition number, it is well known that structured condition numbers (i.e., where only perturbations are taken into account that preserve the structure of the input matrix) might be much smaller than unstructured ones, which, e.g., suggests that structure-preserving algorithms for matrix functions might yield much more accurate results than general-purpose algorithms. In this work, we present a novel upper bound on the structured level-2 condition number, focusing on perturbation matrices within an automorphism group, a Lie or Jordan algebra, or the space of quasi-triangular matrices. In numerical experiments, we then compare the unstructured level-2 condition number with the structured one for some specific matrix functions such as the matrix logarithm, matrix square root, and matrix exponential.

Correlates of felt age in caregivers of people with dementia: findings from the IDEAL study.

Family relationships influence how people appraise their own aging and how their appraisals impact their health. We analyzed felt age (FA) among family caregivers of people with dementia. We used a stratified sample of 1,020 spousal and 202 adult-child caregivers from the IDEAL study. We estimated cross-sectional associations and bidirectional influences between caregivers' FA and their health and wellbeing (depression, number of health conditions, stress, positive aspects of caregiving) over 2 years. Among spousal caregivers, 25% had a younger FA and 36% had an older FA. Among adult-child caregivers, 21.8% had a younger FA and 36.1% had an older FA. In spousal and adult-child caregivers an older FA was cross-sectionally associated with higher depression, number of health conditions, and stress, and fewer positive aspects of caregiving. In spousal caregivers, hours of care per day moderated the association between FA and depression, and FA was associated with stress 1 year later. Caregiving may impact FA and its relationship with health. We urge continued research on the connections between caregiving and FA, and how interventions might support caregivers' positive views on their own aging, which will translate views on aging scholarship to meaningfully improve caregivers' lives.

Vitamin D and human health: evidence from Mendelian randomization studies.

We summarized the current evidence on vitamin D and major health outcomes from Mendelian randomization (MR) studies. PubMed and Embase were searched for original MR studies on vitamin D in relation to any health outcome from inception to September 1, 2022. Nonlinear MR findings were excluded due to concerns about the validity of the statistical methods used. A meta-analysis was preformed to synthesize study-specific estimates after excluding overlapping samples, where applicable. The methodological quality of the included studies was evaluated according to the STROBE-MR checklist. A total of 133 MR publications were eligible for inclusion in the analyses. The causal association between vitamin D status and 275 individual outcomes was examined. Linear MR analyses showed genetically high 25-hydroxyvitamin D (25(OH)D) concentrations were associated with reduced risk of multiple sclerosis incidence and relapse, non-infectious uveitis and scleritis, psoriasis, femur fracture, leg fracture, amyotrophic lateral sclerosis, anorexia nervosa, delirium, heart failure, ovarian cancer, non-alcoholic fatty liver disease, dyslipidemia, and bacterial pneumonia, but increased risk of Behçet's disease, Graves' disease, kidney stone disease, fracture of radium/ulna, basal cell carcinoma, and overall cataracts. Stratified analyses showed that the inverse association between genetically predisposed 25(OH)D concentrations and multiple sclerosis risk was significant and consistent regardless of the genetic instruments GIs selected. However, the associations with most of the other outcomes were only pronounced when using genetic variants not limited to those in the vitamin D pathway as GIs. The methodological quality of the included MR studies was substantially heterogeneous. Current evidence from linear MR studies strongly supports a causal role of vitamin D in the development of multiple sclerosis. Suggestive support for a number of other health conditions could help prioritize conditions where vitamin D may be beneficial or harmful.

Surgical treatment of Ahmed glaucoma valve’s tube protrusion relapse. Clinical observations

In the practice of an ophthalmic surgeon, patients with a large number of concomitant conditions after repeated surgical interventions are seen with increasingly frequency. One of the grave complications in such patients is secondary glaucoma with a refractory type of course. After successful compensation of intraocular pressure in such patients, the risk of complications increases many times, for example, protrusion of the Ahmed valve drainage tube, which becomes the entrance gate for infection, which can lead to endophthalmitis. This article presents clinical cases of surgical treatment of recurrent protrusion of the Ahmed valve drainage tube.

Evaluation of late effects during a 21-year follow-up of pediatric Hodgkin lymphoma survivors: Experience of a pediatric cancer center in Turkey, as a developing country model.

Long-term survivors of Hodgkin lymphoma (HL) are at risk of developing a range of late effects, with a second malignant neoplasm and cardiovascular diseases being the leading causes of death in these patients. The present study aims to evaluate the late side effects in children with HL. Out of 53 HL patients, we assessed the long-term effects of childhood HL survivors (HLSs; n = 50) diagnosed between 1998 and 2019. Patient data related to chronic health conditions, and sociodemographic characteristics were compared with their siblings (n = 56). The cumulative overall survival (OS) at 1, 5, and 10 years from diagnosis was 98.1 ± 1.9%, 93.3 ± 3.8%, and 93.3 ± 3.8%, respectively. Groups of HLSs and their siblings were matched according to age and gender. Compared with siblings, survivors had will be changed as 'a higher frequency of nephrotoxicity (P = 0.02)', cardiotoxicity (P = 0.12), thyroid dysfunction (P = 0.001), health care service usage (P < 0.01), limitation of physical function (P = 0.01), and pulmonary disease (P = 0.01). The control group of siblings had a higher incidence of marital status (P < 0.01), parenthood (P = 0.01), and smoking habit (P = 0.03). Thyroid dysfunction was associated with neck radiotherapy (P < 0.01). No secondaryneoplasm was detected. In relapsed, refractory setting (n = 10), autologous transplantation (n = 9) is performed after a complete remission. Brentuximab vedotin with or without bendamustine and rituximab is also used in selected patients. Increased number of chronic health conditions and social problems point to the significance of long-term follow-up of HLSs. We are currently preparing a survivorship guideline appropriate for Turkey's conditions. Renal, heart, pulmonary impairment, thyroid dysfunction, limitation in physical functioning, and deterioration in social status (marriage, having children, education).

Optimized configuration for liquid crystal Stokes polarimeters in the presence of fast-axis orientation errors.

We present an optimal configuration for Stokes polarimeters based on liquid crystal variable retarders, with the minimum number of measurements. Due to the inherent variations of the director orientation of the liquid crystal molecules, we propose a configuration that minimizes the sensibility of the polarimeter to fast-axis variations. For the optimization we consider a scheme that maximizes the volume of a tetrahedron inscribed in the Poincare sphere, to address additive and Poisson noise, with one of the vertices invariant to changes in the axis positions. We provide numerical simulations, considering misalignment errors, to analyze the robustness of the configuration. The results show that the proposed configuration helps to maintain the volume enclosed by the tetrahedron with high tolerance to fast-axis orientation errors. The condition number will remain below 3.07 for common misalignment errors and below 1.88 for more controlled liquid crystals. This optimization will improve the performance of liquid crystals polarimeters, with a more robust configuration that also considers misalignment errors, beyond additive and Poisson noise.

Imposing different boundary conditions for thermal computational homogenization problems with FFT‐ and tensor‐train‐based Green's operator methods

AbstractTo compute the effective properties of random heterogeneous materials, a number of different boundary conditions are used to define the apparent properties on cells of finite size. Typically, depending on the specific boundary condition, different numerical methods are used. The article at hand provides a unified framework for Lippmann–Schwinger solvers in thermal conductivity and Dirichlet (prescribed temperature), Neumann (prescribed normal heat flux) as well as periodic boundary conditions. We focus on the explicit jump finite‐difference discretization and discuss different techniques for computing the discrete Green's operator. These include Fourier‐type methods, that is, based on discrete sine, cosine and Fourier transformations, as well as low‐rank tensor methods, that is, the tensor‐train approximation, whose computational prowess was demonstrated recently. We use the developed computational technology to investigate a number of interesting random materials and assess different microstructure‐generation techniques in terms of their compatibility with the prescribed boundary conditions.