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Abstract Background The generalized estimating equation (GEE) method is widely used for analyzing longitudinal and clustered data. Although the GEE estimate for regression coefficients and sandwich covariance estimate are consistent regardless of the choice of covariance structure, they are generally biased for small sample sizes. Various researchers have proposed modified GEE methods and covariance estimators to handle small-sample bias. Results We briefly present bias-corrected and penalized GEE methods, along with 11 bias-adjusted covariance estimators. In addition, we focus on analyzing longitudinal or clustered data with binary outcomes using the logit link function and introduce package geessbin in R to implement conventional and modified GEE methods with bias-adjusted covariance estimators. Finally, we illustrate the implementation and detail a usage example of the package. The package is available from the Comprehensive R Archive Network (CRAN) at https://cran.r-project.org/web/packages/geessbin/index.html . Conclusions The geessbin package provides three GEE estimates with numerous covariance estimates. It is useful for analyzing correlated data such as longitudinal and clustered data. Additionally, the geessbin is designed to be user-friendly, making it accessible to non-statisticians.

Background: Intestinal bacteria may play a role in the development of food allergies. This study aimed to analyze and compare the gut microbiota of food-allergic children with that of healthy children of the same age. Methods: Stool samples were collected from one-and-a-half-year-old food-allergic (FA group, n = 29) and healthy controls (HC group, n = 19). A questionnaire was provided to examine the children's birth, dietary, medical, and social histories. The gut microbiota was profiled by 16S rRNA sequencing. Differences in taxonomic composition were assessed using linear discriminant analysis effect size (LEfSe), and microbial functional profiles were predicted with Tax4Fun2. Results: No significant difference in the alpha diversity index between the two groups; however, a negative correlation was observed between the Shannon diversity index and the relative abundance of Bacteroides. A significant difference was observed in beta diversity (permutational multivariate analysis of variance) in the bacterial composition between the FA and HC groups (P 2). The FA group showed a predicted increase in the expression levels of genes associated with intestinal pathogenicity compared with that in the HC group. Conclusions: The gut microbiota of food-allergic children has a higher abundance of bacteria involved in intestinal inflammation and a lower abundance of bacteria involved in immune tolerance than that of healthy children. This dysbiosis may also be associated with food allergies.

Leucine-rich repeat kinase 2 (LRRK2) is the most common gene responsible for familial Parkinson's disease (PD). The gene product of LRRK2 contains multiple protein domains, including armadillo repeat, ankyrin repeat, leucine-rich repeat (LRR), Ras-of-complex (ROC), C-terminal of ROC (COR), kinase, and WD40 domains. In this study, we performed genetic screening of LRRK2 in our PD cohort, detecting sixteen LRRK2 rare variants. Among them, we selected seven variants that are likely to be familial and characterized them in terms of LRRK2 protein function, along with clinical information and one pathological analysis. The seven variants were S1120P and N1221K in the LRR domain; I1339M, S1403R, and V1447M in the ROC domain; and I1658F and D1873H in the COR domain. The kinase activity of the LRRK2 variants N1221K, S1403R, V1447M, and I1658F toward Rab10, a well-known phosphorylation substrate, was higher than that of wild-type LRRK2. LRRK2 D1873H showed enhanced self-association activity, whereas LRRK2 S1403R and D1873H showed reduced microtubule-binding activity. Pathological analysis of a patient with the LRRK2 V1447M variant was also performed, which revealed Lewy pathology in the brainstem. No functional alterations in terms of kinase activity, self-association activity, and microtubule-binding activity were detected in LRRK2 S1120P and I1339M variants. However, the patient with PD carrying LRRK2 S1120P variant also had a heterozygous Glucosylceramidase beta 1 (GBA1) L444P variant. In conclusion, we characterized seven LRRK2 variants potentially associated with PD. Five of the seven variants in different LRRK2 domains exhibited altered properties in kinase activity, self-association, and microtubule-binding activity, suggesting that each domain variant may contribute to disease progression in different ways.

Abstract Background Postoperative delirium (POD) is a complication after surgery which leads to worse outcomes. The frequency of this syndrome is increasing as more elderly patients undergo major surgery. The frequency is around 10–25% but reaches as high as 50% for cardiac surgery. Although intranasal insulin (INI) administration of up to 160 units in patients with cognitive dysfunction and delirium has been shown to improve memory function and brain metabolism without complications such as hypoglycemia, it remains unknown whether INI prevents POD after cardiac surgery Methods A multicenter, double-blind, randomized, controlled trial will be conducted at University of Tsukuba Hospital and Tsukuba Medical Center Hospital, Japan, from July 1, 2023, to December 31, 2025. A total of 110 elderly patients (65 years old or older) undergoing cardiac surgery requiring cardiopulmonary bypass will be enrolled and randomly allocated to intranasal insulin or intranasal saline groups. The primary outcome is the incidence of POD within 7 days after surgery. Secondary outcomes include days and times of delirium, screening tests of cognitive function, pain scores, duration of postoperative tracheal intubation, and length of ICU stay. Discussion The present objective is to assess whether 80 IU INI administration during surgery prevents POD after cardiac surgery. The results may provide strategic choices to prevent POD in patients with cardiac surgery requiring cardiopulmonary bypass. Trial registration The trial was registered with the Japan Registry for Clinical Trials with identifier jRCTs031230047 on April 21, 2023.

To determine the intracellular behavior of p62, a marker of selective autophagy, in oral potentially malignant disorders (OPMDs). This retrospective study includes 70 patients who underwent biopsy or surgical resection and were definitively diagnosed with OPMDs. Immunohistochemical staining for p62, XPO1, p53, and ki67 was performed on all samples and positive cell occupancy was calculated. We statistically investigated the correlation between protein expression in OPMDs and the association between malignant transformation, clinicopathological characteristics, and occupancy. ki67 expression was negatively correlated with p62 expression in the nucleus (p < 0.01) and positively correlated with p62 expression in the cytoplasm (p < 0.01). For malignant transformation, the expression of p62 in the nucleus (p = 0.03) was significantly lower in malignant transformation cases, whereas the expression of p62 in the cytoplasm (p = 0.03) and the aggregation expression (p < 0.01) were significantly higher. Our results suggest that the function of p62 is altered by its subcellular localization. In addition, defects in selective autophagy occur in cases of malignant transformation, suggesting that p62 is a potential biomarker of the risk of malignant transformation of OPMDs.

Background and Objectives: Bedridden patients are at a high risk of venous thromboembolism (VTE). Passive devices such as elastic compression stockings and intermittent pneumatic compression are common. Leg exercise apparatus (LEX) is an active device designed to prevent VTE by effectively contracting the soleus muscle and is therefore expected to be effective in preventing disuse of the lower limbs. However, few studies have been conducted on the kinematic properties of LEX. Therefore, this study aimed to compare the exercise characteristics of LEX with those of an ergometer, which is commonly used as a lower-limb exercise device, and examine its effect on the two domains of muscle activity and circulatory dynamics. Materials and Methods: This study used a crossover design in which each participant performed both exercises to evaluate the exercise characteristics of each device. Fifteen healthy adults performed exercises with LEX and an ergometer (Terasu Erugo, SDG Co., Ltd., Tokyo, Japan) for 5 min each and rested for 10 min after each exercise. Muscle activity was measured using surface electromyography (Clinical DTS, Noraxon, Scottsdale, AZ, USA), and circulatory dynamics were recorded using a non-invasive impedance cardiac output meter (Physioflow Enduro, Manatec Biomedical, Paris, France). The primary outcome was the mean percentage of maximum voluntary contraction (%MVC) of the soleus muscle during exercise. Results: The mean %MVC of the soleus muscle was significantly higher in the LEX group, whereas no significant differences were observed across the periods and sequences. Heart rate, stroke volume, and cardiac output increased during exercise and decreased thereafter; however, the differences between the devices were not significant. Conclusions: LEX may not only have a higher thromboprophylaxis effect, but also a higher effect on preventing muscle atrophy as a lower-extremity exercise device. Additionally, LEX could potentially be used safely in patients who need to be monitored for changes in circulatory dynamics.

Introduction: For assessing drug safety using spontaneous reporting system databases, quantitative measurements, such as proportional reporting rate (PRR) and reporting odds ratio (ROR), are widely employed to assess the relationship between a drug and a suspected adverse drug reaction (ADR). The databases contain numerous ADRs, and the quantitative measurements need to be calculated by performing the analysis multiple times for each ADR. We proposed a novel, simple, and easy-to-implement method to estimate the PRR and ROR of multiple ADRs in a single analysis using a generalized mixed-effects model for signal detection.Methods: The proposed method simultaneously analyzed the association between any drug and numerous ADRs, as well as estimated the PRR and ROR for a specific combination of drugs and suspected ADRs. Furthermore, the proposed method was applied to detect drug-drug interactions associated with the concurrent use of two or more drugs.Results and discussion: In our simulation studies, the false-positive rate and sensitivity of the proposed method were similar to those of the traditional PRR and ROR. The proposed method detected known ADRs when applied to the Food and Drug Administration Adverse Event Reporting System database. As an important advantage, the proposed method allowed the simultaneous evaluation of several ADRs using multiple drugs.

Study Design This is a single-center retrospective cohort study with a university hospital setting. Purpose This study aims to evaluate the short-term course of physical function and walking ability after intramedullary spinal cord tumor (ISCT) resection and predict walking independence 1 year after surgery. Overview of Literature Although several reports have shown the postoperative functional prognosis of spinal intramedullary tumors with long-term follow-up, no reports have identified the predictors associated with the functional outcome at an early stage. Methods A total of 79 individuals who underwent ISCT resection at our institute between 2014 and 2019 were enrolled in the study, whose preoperative walking state was independent ambulator regardless of cane support with the Functional Independence Measure Locomotor Scale (FIM-L) score of ≥6. The FIM-L, the American Spinal Injury Association (ASIA) motor and sensory scores in the lower extremities, and the Walking Index for Spinal Cord Injury II (WISCI II) were assessed for walking independence, lower-limb function, and walking ability, respectively. These evaluations were performed at 4 time points: preoperatively, 1 week (1W), 2 weeks (2W), and 1 year after surgery. Results In the early phase after surgery, 71% and 43% of the participants were nonindependent ambulators at 1W and 2W, respectively. Histopathology indicated that patients with solid tumors (ependymoma, astrocytoma, or lipoma) showed significantly lower indices at 1W and 2W than those with vascular tumors (hemangioblastoma or cavernous hemangioma). Regarding tumor location, thoracic cases exhibited poorer lower-limb function at 1W and 2W and poorer walking ability at 2W than cervical cases. According to the receiver operating characteristic (ROC) analysis, 2 WISCI II points at 2W had the highest sensitivity (100%) and specificity (92.2%) in predicting the level of walking independence at 1 year postoperatively (the area under the ROC curve was 0.99 (95% confidence interval, 0.93–1.00). Conclusions The higher the lower-limb function scores in the early phase, the better the improvement in walking ability is predicted 1 year after ISCT resection.

We have proposed highly efficient microcavity wavelength conversion devices that do not utilize the birefringence or ferroelectricity of crystals. In this study, we utilized a low-birefringence paraelectric SrB _4 O _7 crystal with significant potential for wavelength conversion and high transparency down to 130 nm and succeeded in achieving 199 nm vacuum-ultraviolet second harmonic generation (SHG) with a picosecond laser. The wavelength of 199 nm is shorter than the theoretical minimum for SHG in BaB _2 O _4 of 205 nm. Our device could be a practical vacuum-ultraviolet SHG device, enabling significantly smaller and more efficient vacuum-ultraviolet laser sources compared to conventional systems.

Abstract Aim To investigate the cognitive function and its relation to the home discharge of patients following subacute stroke. Methods This retrospective cohort study included 1,229 convalescent patients experiencing their first subacute stroke. We determined discharge destination and demographic and clinical information. We recorded the following measurement scores: Mini-Mental State Examination (MMSE) score, Stroke Impairment Assessment Set score, grip strength, and Functional Independence Measure (FIM). We performed a multivariable logistic regression analysis with the forced-entry method to identify factors related to home discharge. Results Of the 1,229 participants (mean age: 68.7 ± 13.5 years), 501 (40.8%), 735 (59.8%), and 1,011 (82.3%) were female, had cerebral infarction, and were home discharged, respectively. Multivariable logistic regression analysis revealed that age (odds ratio [OR], 0.93; 95% confidence interval [CI], 0.91 – 0.96; P

Summary: Some Parkinson’s disease (PD)-causative/risk genes, including the PD-associated kinase leucine-rich repeat kinase 2 (LRRK2), are involved in membrane dynamics. Although LRRK2 and other PD-associated genes are believed to regulate synaptic functions, axonal transport, and endolysosomal activity, it remains unclear whether a common pathological pathway exists. Here, we report that the loss of Lrrk, an ortholog of human LRRK2, leads to the accumulation of the lysosome-related organelle regulator, Arl8 along with dense core vesicles at the most distal boutons of the neuron terminals in Drosophila. Moreover, the inactivation of a small GTPase Rab3 and altered Auxilin activity phenocopied Arl8 accumulation. The accumulation of Arl8-positive vesicles is UNC-104-dependent and modulated by PD-associated genes, Auxilin, VPS35, RME-8, and INPP5F, indicating that VPS35, RME-8, and INPP5F are upstream regulators of Lrrk. These results indicate that certain PD-related genes, along with LRRK2, drive precise neuroaxonal transport of dense core vesicles.

Study Design Single-center retrospective study. Purpose We aimed to explore the postoperative prognostic factors for spinal intramedullary ependymoma. Overview of Literature Ependymoma (World Health Organization grade II) is the most frequent intramedullary spinal tumor and is treated by total resection. However, postoperative deterioration of motor function occasionally occurs. Methods Eighty patients who underwent surgical resection at Keio University and Fujita Health University in Tokyo, Japan between 2003 and 2015 with more than 2 years of follow-up were enrolled. A good surgical result was defined as an improvement in the modified McCormick Scale score by one grade or more or having the same clinical grade as was observed preoperatively. Meanwhile, a poor result was defined as a reduction in the McCormick Scale score of one grade or more or remaining in grade IV or V at final follow-up. Univariate and multivariate logistic regression analyses of the following factors were performed in the two groups: sex, age, preoperative Visual Analog Scale (VAS), tumor location, the extent of tumor resection, hemosiderin caps, cavity length, and tumor length on magnetic resonance imaging. Results At final follow-up, 15 patients were included in the poor results group and 65 in the good results group. In the univariate analysis, the factors related to poor results were as follows: higher age, preoperative McCormick Scale score severity, higher preoperative VAS, thoracic location, hemosiderin capped, and non-gross total resection (GTR). A multiple logistic regression analysis was conducted and showed that age, worse preoperative McCormick Scale score, and non-GTR were significant factors for poor prognosis. Conclusions The independent risk factors for motor deterioration after ependymoma resection were age, worse preoperative McCormick Scale score, and non-GTR. Early surgery for patients with even mild neurological disorders could facilitate functional outcomes. These results may contribute to determining the optimal timing of surgery for spinal intramedullary ependymoma.

Abstract Background The Response Evaluation Criteria in Solid Tumors (RECIST) for computed tomography (CT) is preoperatively used to evaluate therapeutic effects. However, it does not reflect the pathological treatment response (PTR) of pancreatic ductal adenocarcinoma (PDAC). The Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST) for positron emission tomography (PET)/CT is effective in other cancers. This study aimed to confirm the usefulness of PERCIST and the prognostic utility of PET/CT for PDAC. Methods Forty‐two consecutive patients with PDAC who underwent neoadjuvant therapy (NAT) and pancreatectomy at our institution between 2014 and 2018 were retrospectively analyzed. We evaluated the treatment response and prognostic significance of PET/CT parameters and other clinicopathological factors. Results Twenty‐two patients who underwent PET/CT both before and after NAT with the same protocol were included. RECIST revealed stable disease and partial response in 20 and 2 cases, respectively. PERCIST revealed stable metabolic disease, partial metabolic response, and complete metabolic response in 8, 9, and 5 cases, respectively. The PTR was G3, G2, and G1 in 8, 12, and 2 cases, respectively. For comparing the concordance rates between PTR and each parameter, PERCIST (72.7% [16/22]) was significantly superior to RECIST (36.4% [8/22]) (P = .017). The area under the curve survival values of PET/CT parameters were 0.777 for metabolic tumor volume (MTV), 0.500 for maximum standardized uptake value, 0.554 for peak standardized uptake value corrected for lean body mass, and 0.634 for total lesion glycolysis. A 50% cut‐off value for the MTV reduction rate yielded the largest difference in survival between responders and nonresponders. On multivariate analysis, MTV reduction rates

Abstract In recent years, a concept of renal rehabilitation has become widely known among nephrology specialists, dialysis specialists, kidney transplantation specialists, rehabilitation specialists, nutrition specialists, guideline specialists, nurses, physiotherapists, and representatives of patients. Therefore, in order to make it clear the definition, methods, and effectiveness of renal rehabilitation in Japan, we launched Renal Rehabilitation Guideline Preparation Committee in 2016 as a part of works in the Japanese Society of Renal Rehabilitation, and created a guideline in accordance to the “Minds Handbook for Clinical Practice Guideline Development 2014”. Here, we report systematic reviews and recommendations of exercise therapies in patients with kidney diseases based on the guideline preparation committee works. Six recommendations for the condition of each kidney disorder, groups addressing nephritis/nephrosis, chronic kidney diseases, dialysis therapy, and kidney transplantation were created. All the recommendation grades were determined by a consensus conference participated in by representatives of patients and various professionals. The purpose of this report is to provide an evidence-based, best practice summary to optimize the quality, safety and efficacy, and availability of renal rehabilitation service, and to provide care for maximum patient prognosis, quality of life, and satisfaction.

Background: Somatosensory impairment is common in patients who have had a stroke and can affect their motor function and activities of daily living (ADL). Therefore, detecting and treating somatosensory impairments properly is considered to be very important, and various examinations have been developed. However, the reliability and validity of few of them have been verified due to differences in the procedure of each examiner or poor quantification by the examination itself.Objective: We hypothesized that, with fixed procedures two convenient clinical examinations, the Semmes-Weinstein Monofilament Test (SWMT) and the Thumb Localizing Test (TLT), could provide reliable assessments of light touch sensation and proprioception. The purpose of this study was to verify the reliability and validity of these two examinations as indices of somatosensory impairment of the upper extremity (UE) in patients with chronic post-stroke hemiparesis.Methods: Fifty patients with chronic stroke (median time after onset of stroke, 848 [474–1708] days, mean age 57 [standard deviation 14] years) were enrolled at Keio University Hospital from 2017 to 2018. Examiners learned the original method of the SWMT and the TLT rigorously and shared it with each other. The TLT procedure was partially modified by dividing the location of the patient's thumb into four spaces. Two examiners evaluated the SWMT and the TLT for 2 days, and intra-rater and inter-rater reliabilities were calculated using weighted kappa statistics. In addition to this, the evaluator size score of the SWMT was assessed with Bland-Altman analysis to evaluate systematic bias. The Stroke Impairment Assessment Set (SIAS) sensory items were used to assess validity, and Spearman's rank correlation coefficients were calculated.Results: Intra/inter-rater agreements of the SWMT grade score were 0.89 (thumb, 95%CI: 0.83–0.95)/ 0.75 (0.60–0.91) and 0.80 (index finger, 0.67–0.93)/0.79 (0.66–0.92), and of the TLT they were 0.83 (navel level proximal space, 0.71–0.95)/ 0.83 (0.73–0.92), 0.90 (navel level distal space, 0.85–0.96)/ 0.80 (0.69–0.90), 0.80 (shoulder level proximal space, 0.68–0.92)/ 0.77 (0.65–0.89), and 0.87 (shoulder level distal space, 0.80–0.93)/ 0.80 (0.68–0.92) (P < 0.001, each item). All of them showed substantial agreement, but the MDC of the SWMT evaluator size was 1.28 to 1.79 in the inter-rater test and 1.94–2.06 in the intra-rater test. The SWMT grade score showed a strong correlation with the SIAS light touch sensation item (r = 0.65, p < 0.001), as did the TLT with the SIAS position sense item (r = −0.70–0.62, p < 0.001 each space).Conclusions: The reliability and validity of the SWMT and the TLT were verified. These tests can be used as reliable sensory examinations of the UE in patients with chronic stroke, and especially for the SWMT, it is more reliable for screening.

[This corrects the article DOI: 10.1371/journal.pone.0246456.].

Food intake biomarkers can be critical tools that can be used to objectively assess dietary exposure for both epidemiological and clinical nutrition studies. While an accurate estimation of food intake is essential to unravel associations between the intake and specific health conditions, random and systematic errors affect self-reported assessments. This study aimed to clarify how habitual food intake influences the circulating plasma metabolome in a free-living Japanese regional population and to identify potential food intake biomarkers. To achieve this aim, we conducted a cross-sectional analysis as part of a large cohort study. From a baseline survey of the Tsuruoka Metabolome Cohort Study, 7,012 eligible male and female participants aged 40-69 years were chosen for this study. All data on patients' health status and dietary intake were assessed via a food frequency questionnaire, and plasma samples were obtained during an annual physical examination. Ninety-four charged plasma metabolites were measured using capillary electrophoresis mass spectrometry, by a non-targeted approach. Statistical analysis was performed using partial-least-square regression. A total of 21 plasma metabolites were likely to be associated with long-term food intake of nine food groups. In particular, the influential compounds in each food group were hydroxyproline for meat, trimethylamine-N-oxide for fish, choline for eggs, galactarate for dairy, cystine and betaine for soy products, threonate and galactarate for carotenoid-rich vegetables, proline betaine for fruits, quinate and trigonelline for coffee, and pipecolate for alcohol, and these were considered as prominent food intake markers in Japanese eating habits. A set of circulating plasma metabolites was identified as potential food intake biomarkers in the Japanese community-dwelling population. These results will open the way for the application of new reliable dietary assessment tools not by self-reported measurements but through objective quantification of biofluids.

Temperature-dependent electroluminescence measurements are performed for 265-nm AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) grown on AlN substrates. The external quantum efficiency (EQE) increases as the temperature decreases from 293 K to 6 K. Using two assumptions, the internal quantum efficiency (IQE) and current injection efficiency (CIE) are unity at the peak EQE at 6 K and the light extraction efficiency is independent of current and temperature, the current and temperature dependences of the product (IQE × CIE) are derived. The temperature dependence of the EQE cannot be simply explained by the Auger recombination processes. This observation enables the CIE and IQE to be separately extracted by rate equation analysis. The room-temperature EQE of the AlGaN-based DUV LEDs is limited by the CIE and not the IQE. We propose that the relatively low CIE may originate from the nonradiative recombination process outside quantum-well layers.

Background and Purpose: Limited research has been conducted with the aim of understanding which upper extremity movements are difficult for persons with severe chronic stroke. The purpose of this study was to test the structure of the Fugl-Meyer Assessment for Upper Extremity (FMA-UE) using Rasch analysis in persons with chronic stroke with moderate to severe deficits and to determine the item difficulty hierarchy.Methods: This was a secondary analysis of data from previous randomized, controlled trials, or clinical trials. The participants were 101 persons with chronic stroke with moderate to severe hemiparesis (time after onset of stroke, 1375.3 ± 1157.9 days; the 33-item FMA-UE, 31.1 ± 12.8). Principal component analysis and infit statistics were used to evaluate dimensionality. Rasch analysis using a rating scale model was performed, and item difficulty was determined.Results: Six misfit items were removed. The results showed that the 27-item FMA-UE was unidimensional. Rasch analysis showed that the movements performed within synergies were among the easiest items. Shoulder and elbow movements were among the easiest items, whereas forearm and wrist movements were among the moderately to most difficult items. Hand items spanned various difficulty levels.Discussion and Conclusions: The FMA-UE is a valid assessment tool of upper extremity motor function in persons with chronic stroke with moderate to severe deficits. The results showed that item difficulty was consistent with the stepwise recovery course proposed by Fugl-Meyer. The movements that are difficult for patients with moderate to severe chronic paresis were determined, which would enable comparison of each movement using a measure of motion difficulty in future studies.

The impact of a face-to-face annealed sputtered AlN/sapphire (FFA Sp-AlN) template with threading-dislocation densities (TDDs) of 2 × 108 cm−2 and an n-type AlGaN (n-AlGaN) underlayer on optical properties of AlGaN multiple quantum wells (MQWs) with an ultraviolet C (UVC) emission is investigated comprehensively. For comparison of the FFA Sp-AlN template with low TDDs, a conventional MOVPE (metalorganic vapor phase epitaxially)-grown AlN/sapphire (MOVPE-AlN) template with TDDs of 1 × 109 cm−2 was prepared. Consequently, cathodoluminescence (CL), temperature-dependent photoluminescence (PL), and time-resolved PL (TR-PL) measurements verified that both the FFA Sp-AlN template and n-AlGaN underlayer are indispensable for obtaining MQWs with high internal quantum efficiencies, which decrease the TDDs and point defect (PD) densities. Our results revealed that 10-period quantum wells (10QWs)/n-AlGaN/AlN grown on the FFA Sp-AlN template exhibit a lower dark spot density in CL panchromatic intensity maps, a higher integrated emission intensity ratio from the temperature-dependent PL (from 15 to 300 K), and a longer nonradiative lifetime from the TR-PL measurements at 300 K compared with those grown on the MOVPE-AlN template. Moreover, we found that the optical properties of 10QWs/AlN in FFA Sp-AlN and MOVPE-AlN templates do not exhibit a significant difference because of the existence of numerous PDs. Our experimental results demonstrate the favorable impact of the FFA Sp-AlN template for low-TDDs and the n-AlGaN underlayer for low-PDs, which holds promise for highly efficient AlGaN deep-ultraviolet light-emitting devices.

Deep-ultraviolet (DUV) microscopy and microspectroscopy have received much attention in label-free live-cell imaging, selective molecular analysis, and optical characterizations of ultrawide bandgap materials. Far-field optics approaches usually suffer from the diffraction limit of light. Meanwhile, near-field optics technology is immature in the DUV spectral region. Herein, we develop a DUV scanning near-field optical microscope (SNOM) with an excitation wavelength of 210 nm. The fourth harmonic generation of a continuous-wave Ti:sapphire laser is the excitation source. Two negative feedback control systems stabilize the power and pointing, allowing scanning microscopy to be carried out over a long period of time even in the DUV spectral region. A reflective objective couples the excitation beam onto an optical fiber probe. The optical fiber probe is solarization-resistant and is not coated by metallic materials. The reflective-based objective optical design does not introduce chromatic aberrations in the detection signals. Our DUV-SNOM is used to measure the photoluminescence (PL) spectra of the quantum well structure of aluminum gallium nitride, which is an ultrawide bandgap material. The PL mapping images indicate that emissive localization centers can be individually visualized via our DUV-SNOM with a lateral resolution exceeding 150 nm.