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It is unclear whether women have a higher risk of stroke than men. This study aimed to clarify the effects of a sex difference on the risk of ischaemic stroke in patients with atrial fibrillation (AF).Health check and insurance claims data were used of people who were aged75 years from 2005 to 2017 in Japan. Patients with AF who were not on anticoagulation therapy were identified. After excluding patients with artificial valves (n=28), haematological disease (n=1,124), aged ≤20 years (n=207), and taking anticoagulant therapy (n=11,848), 9,733 remained for inclusion into the study. The primary outcome was hospital admission due to ischaemic stroke.Of the 9,733 participants, 7,079 (72.7%) were men. The mean age of women (54.4 years) was significantly higher than that of men (53.2 years). During a mean 2.5-year follow-up period, 143 ischaemic stroke events occurred. Female sex was not associated with ischaemic stroke (adjusted hazard ratio [95% confidence interval]: 1.13 [0.78-1.66]). When stratified using the CHAIn this large-scale, real-world study of patients with AF, the risk of ischaemic stroke among those aged75 years was comparable between women and men. These findings are consistent with the current guidelines, which do not recommend anticoagulant therapy for women with no other risk factors (CHA

The aim of this study was to investigate the association between pulse pressure (PP) and chronic kidney disease (CKD) progression among the general population in Japan. We conducted a population-based cohort study of the residents of Iki Island, Nagasaki, Japan, from 2008 to 2018. We identified 1042 participants who had CKD (estimated glomerular filtration rate(eGFR) 2 or the presence of proteinuria) at baseline. Cox’s proportional hazard model was used to evaluate the association between PP and progression of CKD. During a 4.66-year mean follow-up, there were 241 cases of CKD progression (incident rate: 49.8 per 1000 person-years). A significant increase existed in CKD progression per 10 mmHg of PP elevation, even when adjusted for confounding factors [adjusted hazard ratio 1.17 (1.06–1.29) p

We aimed to investigate the association between serum uric acid (SUA) level and development of hypertension as well as the interaction effect of chronic kidney disease (CKD) on this relationship in the general Japanese population. We included 7895 participants aged ≥30 years from the ISSA-CKD study, a population-based retrospective cohort study that used annual health check-up data of residents from Iki Island, Japan. After the exclusion of 1881 with l < 1-year follow-up, 2812 with hypertension at baseline, and 165 with missing information on SUA, a total of 3037 participants were enrolled in this analysis. Participants were divided into four groups according to the quartiles of SUA level at baseline, and multivariable-adjusted hazard ratios for new-onset hypertension were calculated. Stratified analyses were performed for each subgroup (defined by sex, age, alcohol intake, and CKD) to assess the interaction effects. During a mean follow-up period of 4.4 years, 943 participants developed hypertension. The first quartile group was set as the reference group, and the multivariable-adjusted hazard ratios (95% confidence interval) for new-onset hypertension were 1.11 (0.90-1.36) in the second quartile, 1.25 (1.02-1.54) in the third quartile, and 1.35 (1.07-1.70) in the fourth quartile compared with those in the reference group (p = .007 for trend). The stratified analyses showed that the association between SUA and hypertension was significantly stronger in participants with CKD than in those without CKD (p = .035 for interaction). SUA level is an independent risk factor for new-onset hypertension. This tendency was significantly stronger in participants with CKD.

Introduction: Evidence using real-world data is sparse regarding the effects of oral anticoagulants (OACs) among patients with kidney disease. The aim of this study was to investigate the effects of kidney disease on ischemic stroke (IS) or systemic embolism (SE) among patients taking OAC, using large-scale real-world data in Japan. Methods: This was a retrospective cohort study using claims data and health checkup data from health insurance associations in Japan, from January 2005 to June 2017. We enrolled 21,581 patients diagnosed with atrial fibrillation (AF). Of the total population, 11,848 (54.9%) patients were taking OAC. A Cox proportional hazards model was used to examine the effect of kidney disease on IS/SE with or without OAC. Results: During follow-up, 208 participants who were not taking OAC (mean follow-up 2.6 years) and 200 who were taking OAC (mean follow-up 3.0 years) experienced IS/SE. The % IS/SE incidence rates with and without kidney disease were 2.42/person-year and 0.63/person-year in the total population, 3.66/person-year and 0.76/person-year in the group without OAC use, and 1.52/person-year and 0.55/person-year in patients with OAC use, respectively. Hazard ratios (HRs) and 95% confidence intervals (CIs) of kidney disease for IS/SE were high, irrespective of OAC, even after adjustment: adjusted HR 2.62 (95% CI: 1.72–3.99) without OAC and adjusted HR 2.03 (95% CI: 1.20–3.44) with OAC; p = 0.193 for interaction between no OAC and OAC. Although bleeding risk was also high for kidney disease irrespective of OAC use (HR 2.93 [95% CI: 2.27–3.77] in the total population, HR 3.08 [95% CI: 2.15–4.43] in the group without OAC, and HR 2.73 [95% CI: 1.90–3.91] in the group with OAC use), net clinical benefit indicated that the benefit of OAC use exceeded the risk of bleeding: HR 4.50 (95% CI: 0.76–8.23) among those with kidney disease and HR 0.35 (95% CI: 0.04–0.66) among those without kidney disease. Conclusion: Although we found that OAC use was effective and recommended for patients with AF, advanced kidney disease is still an independent risk factor for IS/SE, even in patients taking OAC. Physicians should be aware of this risk and strictly control modifiable risk factors, regardless of OAC use.

ObjectiveAmong patients with atrial fibrillation, the risks of ischaemic stroke and systemic embolism (IS/SE) are high even with effective anticoagulation. Using large-scale, real-world data from Japan, this study aims to clarify residual risks of IS/SE attributable to modifiable risk factors among patients with atrial fibrillation who are taking oral anticoagulants.MethodsThe study design we employed was a retrospective cohort. Health check-ups and insurance claims data of Japanese health insurance companies were accumulated from January 2005 to June 2017. We identified 11 848 participants with atrial fibrillation who were on oral anticoagulants during the study period. We set the modifiable risk factors as hypertension, diabetes and dyslipidaemia. A Cox proportional hazards model was used to obtain the effects of the risk factors for IS/SE.ResultsDuring an average of 3 years’ follow-up, 200 cases of IS/SE occurred (incidence rate 0.57 per 100 person-years). In multivariable analyses, older age (65–74 vs ConclusionAmong patients with atrial fibrillation on anticoagulant therapy, approximately one-third of the residual risks were estimated to be attributable to modifiable risk factors such as hypertension, diabetes and dyslipidaemia.

Background This large‐scale observational study on negative events in a real‐world setting investigated Japanese patients with atrial fibrillation who were not on anticoagulants. This study aims to evaluate the incidence of ischemic stroke and bleeding events (intracranial hemorrhage, gastrointestinal bleeding, others) based on CHA 2 DS 2‐ VAS c scores in Japanese patients with atrial fibrillation who were not anticoagulated. Methods and Results We used health checkups and insurance claim data from a Japanese insurance organization. Altogether, 9733 atrial fibrillation patients were not prescribed anticoagulation during their follow‐up periods. Patients’ risk levels were defined by their CHA 2 DS 2‐ VAS c scores (range 0–≥3): Men with scores of 0, 1, or ≥2 and women with scores of 1, 2, or ≥3 were considered at low, intermediate, or high risk, respectively. Cox proportional hazards model was used to assess the association between the CHA 2 DS 2‐ VAS c‐determined risk and the incidence of ischemic stroke and intracranial, gastrointestinal, and other bleeding. The mean 2.5‐year follow‐up revealed 143 ischemic strokes and 332 bleeding events. Annual event rates were 0.58% for ischemic stroke and 1.17% for total bleeding events. Annual incidence of ischemic stroke increased with elevated predicted risks based on CHA 2 DS 2‐ VAS c scores: 0.18% for low‐risk, 0.44% intermediate‐risk, and 1.29% high‐risk groups ( P P Conclusions Risks of ischemic stroke and bleeding events were high, particularly among those with high CHA 2 DS 2‐ VAS c scores.

AIM The present study aimed to investigate the effects of the 2014 Japanese fee schedule revision on trends in artificial nutrition routes, including gastrostomy, nasogastric tube and parenteral nutrition, among older people with dementia, using time series analysis. METHODS The study used claim data in Japan submitted to Fukuoka Late Elders' Health Insurance from fiscal year 2010 to fiscal year 2016. We identified older people with dementia provided for the first time with artificial nutrition via gastrostomy, nasogastric tube or central venous line and aggregated their data by month. Interrupted time series analyses were used to examine trends in artificial nutrition routes over time. RESULTS The numbers of older people with dementia receiving nutrition via gastrostomy, nasogastric tube and parenterally declined consistently. The slopes for pre-revision trends in gastrostomy, nasogastric tube and parenteral nutrition procedures were all significantly negative in the interrupted time series analyses. The post-revision trends in gastrostomy and parenteral nutrition continuously had significant negative slopes. In contrast, the significant negative trend in nasogastric tube procedures in the pre-revision period had disappeared during the post-revision period. CONCLUSIONS The study showed that the fee schedule revision had limited impact on gastrostomy and parenteral nutrition. However the trend for nasogastric tube was ambiguous; hence, sustainable surveillance is required for evidence-based health policy. Geriatr Gerontol Int 2018; 18: 1405-1409.

Background: The relationship between socioeconomic status (SES) and knowledge of cardiovascular risk factors remains unknown in a general Japanese population. Methods: Of 8,815 participants from 300 randomly selected areas throughout Japan, 2,467 participants who were free of cardiovascular disease and who provided information on SES in the National Health and Nutrition Survey of Japan 2010 were enrolled in this cross-sectional analysis. SES was classified according to the employment status, length of education, marital and living statuses, and equivalent household expenditure (EHE). Outcomes were ignorance of each cardiovascular risk factor (hypertension, diabetes, hypercholesterolemia, low high-density lipoprotein [HDL] cholesterol, arrhythmia, and smoking) and insufficient knowledge (number of correct answers

Objectives: To reveal the effect of age and other factors on perceived anxiety over radiation exposure among decontamination workers in Fukushima Prefecture, Japan. Methods: A survey questionnaire was sent to 1505 workers, with questions regarding age, presence of a written employment contract, previous residence, radiation passbook ownership, presence of close persons for consultation, knowledge of how to access public assistance, and a four-point scale of radiation-related anxiety (1= "Very much," 2= "Somewhat," 3= "A little bit," and 4= "None" ). The relationships between the degree of anxiety and variables were analyzed using the chi-square test and residual analysis. Results: In all, 512 participants responded to the questionnaire. The mean age of participants was 46.2 years (SD: 13.1, range: 18-77). Of them, 50, 233, 168, and 61 workers chose "Very much," "Somewhat," "A little bit," and "None," respectively, on the anxiety scale. Chi-square test showed that participants aged 61 years and over had higher degrees of anxiety (p

Home cooking has been suggested as a key to healthy dietary intakes. However, little is known about the association between cooking behaviour and nutrient intake among young-to-middle-aged women. We aimed to investigate the association between home cooking frequency and nutrient intake adequacy among married Japanese women. Self-administered questionnaires were used to assess the weekly frequency of cooking dinner at home and habitual nutrient intake during the preceding month. We evaluated nutrient intake adequacy by comparing the self-reported intake with two indices of the dietary reference intakes for Japanese (2015): the estimated average requirement (EAR) of fourteen nutrients, and the ‘tentative dietary goal for preventing lifestyle-related diseases’ (DG) of seven nutrients. A total of 143 participants (25–44 years old) completed the questionnaires, with 32·9 % of participants reporting a weekly home cooking frequency of seven times/week. Women with a higher home cooking frequency (seven times/week) were more likely to have children (P = 0·001) than those with a lower home cooking frequency (0–6 times/week). Of the nutrients evaluated, there was no significant difference between the two groups in meeting EAR and DG. Our findings suggest that daily home cooking may not be necessary to achieve adequate nutrient intake, specifically among married, young-to-middle-aged Japanese women.

OBJECTIVES: The aim of this study was to reveal factors related to heat illness in radiation decontamination workers and determine effective preventive measures. METHODS: A self-administered questionnaire was sent to 1,505 radiation decontamination workers. The questionnaire included age, sex, duration of decontamination work, previous occupation, education provided by employers regarding heat illness, preventive action against heat illness, and subjective symptoms of heat illness during work. We included 528 men, who replied and answered all questions, in the statistical analysis. Subjective symptoms of heat illness were categorized as "no symptoms," "Grade I" and "Grade II" according to severity. A multiple linear regression model was used to determine the factors associated with the severity of heat illness. RESULTS: The mean age of the subjects was 47.6 years old (standard deviation: 13.4). Of the 528 workers, 316 (59.8%) experienced heat illness symptoms (213 at Grade I and 103 at Grade II). The results of the stepwise selection revealed that age, outdoor manual labor, adequate sleep, use of a cool vest, and salt intake were selected as preventive factors, whereas living in a company dormitory or temporary housing, wearing light clothing, and consuming breakfast were selected as risk factors for heat illness. CONCLUSIONS: Both working conditions and living environment are associated with heat illness in radiation decontamination workers. Type of housing and sleep are also strongly related to heat illness during work. Employers should consider not only the working conditions of the employee but also the employee's daily living conditions, in order to prevent heat illness. Language: en

Objectives : Nicotine in cigarettes is metabolized primarily by CYP2A6-catalyzed oxi- dation. The CYP2A6*4 allele, in which CYP2A6 is a homozygous whole-deletion variant, com- pletely lacks enzyme activity. The aim of this study was to examine the effects of CYP2A6*4 ge- netic polymorphism on smoking behavior and nicotine dependence in a general population of Japanese men. Methods : The subjects were 124 healthy Japanese men who gave informed consent to give saliva samples. The survey items included general information, smoking behaviors and nicotine depen- dence. The polymerase chain reaction restriction fragment length polymorphism method was used to analyze the genetic polymorphisms of CYP2A6. The subjects were classified into two groups : Group W (CYP2A6*4 absence : *1A/*1A, *1A/*1B and *1B/*1B) and Group D (CYP2A6*4 presence : *1B/*4A, *4A/*4A, *1A/*4A or *1B/*4D, and *1A/*4D). We analyzed the differences in the survey items between the two groups. Results : There were no significant differences in smoking behaviors between the two groups. However, Group D tended to have less difficulty in refraining from smoking after waking in the morning compared to Group W (p=0.051). Conclusions : CYP2A6*4 genetic polymorphisms may not strongly affect smoking behavior but may possibly have an effect on nicotine dependence.

BACKGROUND Nicotine concentration in hair is a useful marker of tobacco exposure. Detection of nicotine in the hair of non-smokers indicates passive smoking. Accurate measurement of nicotine among active and passive smokers can help in smoking cessation programs or programs designed to prevent secondhand smoke exposure. OBJECTIVE To establish, using high-performance liquid chromatography-ultraviolet detection (HPLC/UV), a hair nicotine cut-off value to distinguish active from passive smokers. METHODS Hair samples were collected from randomly chosen Japanese men (n= 192) between 2009 and 2011. Nicotine and cotinine levels in hair were measured using HPLC/UV with column-switching. T-tests and chi-square tests were performed to compare active and passive smokers, while receiver operating characteristic curves were used to evaluate the effectiveness of the cut-off value. RESULTS There were 69 active smokers and 123 passive smokers. The nicotine and cotinine concentrations in hair were significantly higher in active than in passive smokers (p< 0.01). The area under the curve for nicotine was 0.92. A hair nicotine cut-off value of 5.68 ng/mg, with a sensitivity of 94.2% and specificity of 87.0%, was identified as the optimal cut-off value for separating active from passive smokers. CONCLUSION Nicotine and cotinine concentrations in hair clearly distinguished active from passive smokers.

Introduction The purpose of this study was to investigate the diagnostic accuracy of cardiac 123I-metaiodobenzylguanidine (MIBG) scintigraphy for the diagnosis of Parkinson's disease (PD), especially in the early stages. Methods We investigated 600 patients who underwent cardiac 123I-MIBG scintigraphy to diagnose their parkinsonism and/or cognitive impairment. Of 600 research subjects, 272 patients were clinically diagnosed with PD. MIBG uptake was compared between patients with PD and other diseases. Furthermore, the sensitivity and specificity of cardiac 123I-MIBG scintigraphy to diagnose PD was estimated by disease duration ( Results MIBG uptakes of PD patients were significantly decreased compared with those of other diseases except dementia with Lewy bodies and pure autonomic failure (p Conclusion Our findings demonstrated that cardiac 123I-MIBG scintigraphy had sufficient diagnostic accuracy to detect the early phase of PD. Indeed, this study of a large number of patients provides further external validation that MIBG has diagnostic ability to distinguish PD from atypical parkinsonism.

Objectives : From our previous results, manganese (Mn) and iron (Fe) in the blood of Parkinson's disease (PD) patients without depression were higher than those of both the PD patients with depression and controls, the hypothesis that "two types of PD exist-PD without depression and affected by Mn and Fe, and PD with depression and unaffected by Mn or Fe" was induced. To investigate the hypothesis, correlations among blood and urine met- als were compared in the subjects. Methods : Subjects comprised PD patients with de- pression, PD patients without depression and controls recruited from an outpatient clinic in China. Morning blood and urine samples were used to measure concentrations of metals. Results : In the controls, Mn, Fe and zinc (Zn) levels in blood strongly correlated with each other. The correlation coefficient between Mn and Zn in blood was significant in the PD pa- tients with depression and the controls, but not in the PD patients without depression. Cor- relations of Fe between blood and urine in the PD patients without depression were signifi- cant, but not in the PD patients with depression and the controls. Conclusions : A common route of simultaneous intake of Mn, Fe and Zn could exist in our subjects, however in PD patients without depression, a large intake of Mn may have been from another route. Some results of the PD patients without depression were different from those of the PD pa- tients with depression and the controls. Thus, two types of PD may exist.

Objectives Some heavy metals are suspected to be pathogenic to both Parkinson's disease (PD) and depression. Common background may exist in them. Methods Subjects com- prised PD patients with depression, PD patients without depression and controls recruited from the outpatient clinic in China. Morning blood and urine samples were used to measure concentrations of metals and vitamins. Results Whole-blood manganese was significantly higher in the PD patients without depression than in both the PD patients with depression and the controls. Serum iron was significantly higher in the PD patients without depression than in the controls. Urine iron was also significantly higher in the PD patients without depression than in the controls. Serum copper was significantly lower in the PD patients with depression than in both the PD patients with- out depression and the controls. Conclusions Excessive intake of iron and accumulation of man- ganese seemed to be involved in the etiology of non-depressive PD.

The aim of this study is to clarify factors related to premature death among Japanese professional baseball players by a case-control analysis. The subjects are two matching groups of 622 Japan Professional Baseball (JPB) league players, those deceased and those surviving. Cases and controls are matched by birth year. All players debuted on the first string between 1934 and 2003, and are listed in The Official Baseball Encyclopedia of Japan. To compare means and frequencies of characteristics between deceased and surviving groups, t-tests and chi-square tests were used. A logistic regression analysis was assessed contributions of each independent variable on death. Significant differences between deceased and surviving players were observed in this study; deceased players had higher body mass indexes and longer careers. Furthermore, logistic regression analysis confirmed that body mass index and career length were statistically significant determinants of death for baseball players. This is the first report to examine factors of death for professional baseball players except employing data attained from Major League Baseball.

One and a half years have passed since the Fukushima Daiichi nuclear power plant disaster. The environmental radiation dose rate was not critical, but an existing exposure situation has been identified in a large part of Fukushima Prefecture. Although people continue to live and work in the contaminated area, they are not provided with sufficient information to reduce their exposure to radiation by themselves. In this study, we attempt to evaluate the efficiency of radiation shielding by using everyday items widely available to people.NaI scintillation and Geiger-Müller survey meters were used to measure the radiation dose of (1) contaminated soil and (2) soil covered with commonly available items.In the soil at a depth of 10 cm from the surface, the radiation dose rate decreased from 3.36 to 0.65 μSv/h, and the count rate decreased from 3,120 to 352 cpm. Both the radiation dose rate and count rate reduced when the soil was covered with everyday items, such as a magazine more than 20 mm thick, a polystyrene foam board, and a wooden board of the same thickness.To protect residents from unnecessary radiation exposure in the existing exposure situation, covering contaminated soil with a wooden board or a magazine, either of them 20 mm thick, is useful to reduce the radiation dose.

Background & aims Factors associated with depression in Parkinson’s disease, especially lifestyle and nutrition, have been poorly studied. Our study was conducted to investigate nutritional factors associated with depression in Parkinson’s disease. Methods The subjects were 82 Parkinson’s disease patients and the same number of sex and age-matched controls recruited from the outpatient clinic of Xiangfan No. 1 People’s Hospital in Hubei, China between 2006 and 2008. The Parkinson’s disease patients were divided into two groups, 24 Parkinson’s disease with depression and 58 Parkinson’s disease without depression. DSM-IV criteria was used for the primary diagnosis of depressive disorders. The severity of depression in patients was assessed by the criteria of the Hamilton Depression Rating Scale (HAMD-17), and a score ≥14 was defined as “depression”. Information about eating habits and other factors was obtained by subject recall of state prior to diagnosis of Parkinson’s disease and depression Results Compared with the Parkinson’s disease patients without depression and the controls, the Parkinson’s disease patients with depression had relatively low levels of income and education. Fat and vitamin B1 intake was significantly higher in the Parkinson’s disease patients with depression than in both the Parkinson’s disease patients without depression and the controls. Bean product intake was significantly lower in the Parkinson’s disease patients with depression than in both the Parkinson’s disease patients without depression and the controls. Conclusions Less fat and vitamin B1 but more bean product intake might be associated with a lower risk for depression in Parkinson’s disease patients from a higher income bracket with better educational background.

In this paper, we describe high-speed 1.1-μm-range oxide-confined vertical-cavity surface-emitting lasers (VCSELs) for large-scale optical interconnection applications. For achieving high data rates up to 25 Gbit/s under high temperature, we applied InGaAs/GaAsP strain-compensated multiple quantum wells (SC-MQWs) as the active layer. The developed device showed 25 Gbit/s error-free operation at 100°C. We also examined reliability of the VCSELs through accelerated life tests. The result showed an extremely long lifetime of about 10 thousand hours in MTTF under an ambient temperature of 150°C and a current density of about 19 kA/cm2. The level of reliability either equaled or surpassed that of conventional 0.85-μm VCSELs. Moreover, we revealed a typical failure mode of the device, which was caused by ≪110≫ dark line defects (DLDs) generated in the n-DBR layers under the current aperture area.

We have developed InGaAs-based VCSELs operating around 1.1µm for high-speed optical interconnections. By applying GaAsP barrier layers, temperature characteristics were considerably improved compared to GaAs barrier layers. As a result, 25Gbps 100°C error-free operation was achieved. These devices also exhibited high reliability. No degradation was observed over 3, 000 hours under operation temperature of 150°C and current density of 19kA/cm2. We also developed VCSELs with tunnel junctions for higher speed operation. High modulation bandwidth of 24GHz and a relaxation oscillation frequency of 27GHz were achieved. 40Gbps error-free operation was also demonstrated.

Background Quitting smoking is important to reduce smoking-related diseases. What is the difference between people who continue to smoke and those who can quit smoking. We focused on nicotine metabolism. Smokers crave nicotine when their body’s nicotine concentration drops. Therefore, we hypothesized that quick metabolism of nicotine is a contributing factor of continuation of …

This paper reports the planar-structure InAl-GaAs-InAlAs superlattice avalanche photodiodes (SL-APDs) with a Ti-implanted guard-ring, which were developed for a compact and high-sensitivity 10-Gb/s optical receiver application. The design and fabrication of the novel concept planar-structure including the Ti-implanted guard-ring are described. The characteristics of the planar APDs are 0.36 /spl mu/A dark current at a multiplication factor of 10, 67% quantum efficiency, 110-GHz gain-bandwidth (GB) product, 15-GHz top-bandwidth, and - 27.2-dBm sensitivity at 10 Gb/s. The reliability was preliminary tested and the lifetime of longer than 10/sup 7/ h at 50/spl deg/C was estimated. The dark current characteristics including its temperature dependence and the excess noise characteristics are also analyzed. All the obtained characteristics exhibit the practical availability of the planar SL-APDs in the 10-Gb/s trunk line optical receiver uses.

We developed 1.1-mum-range vertical-cavity surface-emitting lasers based on InGaAs-GaAs quantum wells, back-illuminated InGaAs photodiodes, and transimpedance amplifiers (InP heterojunction bipolar transistor) for high-speed optical interconnection. Clear eye opening operation and error-free transmission at 30 Gb/s over 100-m multimode fibers (GI32) were successfully achieved for the first time.

We propose 1.1-µm-range InGaAs quantum-well (QW) vertical-cavity surface-emitting lasers (VCSELs) with a buried type-II tunnel junction (BTJ). Because of the low electrical resistance of the type-II tunnel junction, the chip resistance was reduced by over 40% compared with conventional oxide-confined VCSELs with the same-size aperture. In an aging test, stable operation at 85 °C was maintained in terms of optical and electrical characteristics for over 1000 h without early failure. The introduction of the type-II TJ structure can suppress self-heating caused by the chip resistance and may be a practical approach to achieving high-speed VCSELs for advanced optical interconnection.

We have developed vertical-cavity surface-emitting lasers for optical interconnections operating at 1.07 mum. The active layers of the devices are InGaAs-GaAs multiple quantum-wells, which are suitable for high-speed operation and high reliability. The devices exhibit -3-dB modulation bandwidths up to 19 GHz and no degradation under 70degC, 1000-h automatic power control tests. Error-free 20-Gb/s operations were also achieved

A compositionally graded sawtooth-bandgap multilayer consisting of In 1 − x − y Ga x Al y As lattice-matched to InP was fabricated by low-pressure metalorganic vapor phase epitaxy for reverse-bias device application. Using this multilayer in a staircase avalanche photodiode with a configuration separating the photo-absorption and multiplication regions resulted in a multiplication factor of over 80 and a multiplied dark current of only 2.2 pA/μm 2 . Spectral measurements revealed that the triangular band structure causes the photo-absorption edge red shift due to an electric field to be smaller than that of a rectangular superlattice structure.

InAlGaAs-InAlAs superlattice avalanche photodiodes (SL-APD's) have been designed and experimentally analyzed. The layer structures and the electric field profiles were designed for 10 Gb/s applications. The mesa-structure SL-APD's exhibited a gain-bandwidth product of 120-150 GHz, a top bandwidth of 15 GHz, and a multiplied dark current of 15-20 nA for a mesa-diameter of 30 /spl mu/m. Other characteristics, such as temperature dependence of dark current and dynamic ranges, were also analyzed. Furthermore, an estimated life-time of longer than 10/sup 5/ h was achieved for the first time. The obtained characteristics, especially their high-speed characteristics with their low dark current, indicate potential for 2.5-10 Gb/s high-sensitivity and small optical receiver applications.

Bandgap energy control of a selectively grown InAlAs InGaAs multiple quantum well (MQW) on a mask-patterned planar InP substrate was studied in order to expand device applications using the large conduction band offset of 0.5 eV in the InAlAs InGaAs system. The growth mechanism in the InAlAs selective growth was mainly dominated by gas-phase diffusion through the lateral concentration gradient, like that in InGaAs, and distinguishable segregation of highly active Al species was not observed. The induced strain for the grown InAlAs was characterized to achieve a highly crystalline MQW structure. An extremely wide bandgap energy shift exceeding 350 meV was demonstrated for the selectively grown InAlAs InGaAs MQW without polycrystals on the mask.

Selective MOVPE of InAlGaAs with almost no polycrystalline growth was achieved. The composition change was also observed in selective InAlGaAs growth. The In content is enhanced with wider mask width, which makes the bandgap energy smaller. A large photoluminescence (PL) peak wavelength shift of 170 nm with a mesa width of 2 /spl mu/m and a mask width of 40 /spl mu/m was achieved. This is the first report on bandgap energy control in InAlGaAs selective growth.

The present study was a cross-sectional study conducted to reveal the prevalence of metabolic syndrome and its components and describe the features of such prevalence among Japanese workers by clustered business category using big data. The data of approximately 120,000 workers were obtained from a national representative insurance organization, and the study analyzed the health checkup and questionnaire results according to the field of business of each subject. Abnormalities found during the checkups such as excessive waist circumference, hypertension or glucose intolerance, and metabolic syndrome, were recorded. All subjects were classified by business field into 18 categories based on The North American Industry Classification System. Based on the criteria of the Japanese Committee for the Diagnostic Criteria of Metabolic Syndrome, the standardized prevalence ratio (SPR) of metabolic syndrome and its components by business category was calculated, and the 95% confidence interval of the SPR was computed. Hierarchical cluster analysis was then performed based on the SPR of metabolic syndrome components, and the 18 business categories were classified into three clusters for both males and females. The following business categories were at significantly high risk of metabolic syndrome: among males, Construction, Transportation, Professional Services, and Cooperative Association; and among females, Health Care and Cooperative Association. The results of the cluster analysis indicated one cluster for each gender with a higher prevalence of metabolic syndrome components; among males, a cluster consisting of Manufacturing, Transportation, Finance, and Cooperative Association, and among females, a cluster consisting of Mining, Transportation, Finance, Accommodation, and Cooperative Association. These findings reveal that, when providing health guidance and support regarding metabolic syndrome, consideration must be given to its components and the variety of its prevalence rates by business category and gender.

We have developed 12-channel × 20-Gbps optical transmitter/receiver modules with 9 × 14-mm footprints. To achieve stable optical coupling efficiency, we also developed a precise multi-chip mounting technique. The three dies of 4-channel vertical-cavity surface-emitting laser (VCSEL)/photodiode (PD) arrays are mounted at the same time. The accuracy of the Z-axis can be controlled by monitoring the dies' positions for the optical reference plane. The coupling losses were less than 1.5 dB in the 12-channel transmitter/receiver modules. The standard deviations of the coupling losses were less than 1.0 dB in all samples. Error-free transmissions at a data rate of 20 Gbps were also demonstrated. A reliability test indicated that the modules are repairable and reliable.

We have developed compact 12-channel, on-board optical transmitters and receivers. The assembly size was 9 mm × 14 mm. Error-free transmission up to 20 Gb/s/ch was achieved, which will enable us to construct a high density optical interconnect.

In this paper, we describe high temperature operation of high speed 1.1μm-range oxide-confined vertical-cavity surfaceemitting lasers (VCSELs) for optical interconnection applications. For achieving high speed of over 25 Gbit/s under a high temperature, we applied InGaAs/GaAsP strain-compensated multiple quantum wells (SC-MQWs) as the active layer. The developed device showed 25 Gbit/s error-free operation at 100°C. We also examined reliability of the VCSELs via accelerated life tests. The result showed extremely long MTTF lifetime of about 10 thousand hours under an ambient temperature of 150°C and a bias current of about 19 kA/cm 2 , a reliability that either equals or surpasses that of conventional 850-nm VCSELs with 10 Gbit/s. Moreover, we revealed a typical failure mode of the device; the result of analysis indicated that the failure was caused by dark line defects (DLDs) generated in the n-DBR layers under the current aperture area.

We developed 1.1-mum-range oxide-implant VCSELs with InGaAs/GaAsP strain-compensated MQWs. 25 Gbit/s-100degC error-free operation and high reliability over 3000 hours under 150degC operation were successfully demonstrated.

We have developed 1.1-μm-range high-speed VCSELs based on InGaAs-QWs for high-speed and highly reliable optical interconnections. 3-dB bandwidth up to 20 GHz and error-free 30-Gbps 100 m operations were demonstrated with oxide confined VCSELs. We also developed buried tunnel junction VCSELs to further improve the relaxation oscillation frequency limit. 3-dB bandwidth up to 24 GHz and error-free 40-Gbps operations were demonstrated with these VCSELs.

Recently low-cost optical links for home and car networks have been extensively developed under the continuous need for expanding transmission capability. Popular low-cost optical links based on red-LEDs and 0.85-μm VCSELs mainly handle bit rates below 1 Gbit/s. In this paper, we demonstrate 6 Gbit/s optical data transmission under a wide temperature range from -40 to 115°C, using low-cost plastic-mold Transmitter (Tx) and Receiver (Rx) leadframe modules. The high transmission rate can handle high-definition television signals, and the expanded operating temperature range is applicable even for roof modules in automotive applications.

We demonstrate 30-Gb/s transmission using 1.1 μm-range VCSELs based on InGaAs/GaAs quantum wells, back-illuminated InGaAs PDs, and TIAs (InP-HBT). Error-free 30-Gbps transmission with 100 m-MMFs (GI32) is achieved for the first time.

We developed VCSELs based on InGaAs-QWs for high-speed optical interconnections. Error-free operations were achieved up to 25 Gbps. We also proposed VCSELs with type-II tunnel junctions to reduce electrical resistance for higher speed operation.

We propose 1.1-μm-range VCSELs with buried Type-II tunnel junctions (BTJs). Due to the small electrical resistance of the Type-II tunnel junction, the chip resistance was reduced by half as compared with oxide confined VCSELs. The BTJ-VCSELs were lased up to 120°C.

In this work, 1.1-/spl mu/m-range VCSELs based on InGaAs/GaAs quantum wells with high modulation bandwidth up to 20 GHz were developed. Error-free 25-Gbps operations were achieved for the first time using directly modulated multimode VCSELs.

For compact and high-sensitivity 10 Gb/s optical receiver applications, we have developed low-dark-current planar-structure InAlGaAs-InAlAs superlattice avalanche photodiodes with a Ti-implanted guard-ring. The APDs exhibited dark current as low as 0.36 /spl mu/A at a gain of 10. The temperature dependence of the dark current was confirmed to be in a sufficient level for practical 10-Gb/s applications. The APDs also exhibited a quantum efficiency of 67%, a gain-bandwidth-product of 110 GHz, a top 3-dB bandwidth of 15.2 GHz, and a minimum gain for 10-GHz bandwidth of 1.6. Preliminary aging test also showed a stable dark current operation after aging of over 2200 h at 200/spl deg/C. These high-reliability, low-dark-current, high-speed, and wide-dynamic-range characteristics are promising for 10-Gb/s high-sensitivity optical receiver use.

Summary form only given. In summary, a lifetime over 1.0/spl times/10/sup 5/ hours at 50/spl deg/C was attained by the simple mesa-structure InAlGaAs-InAlAs superlattice avalanche photodiodes (SLAPDs) for the first time. This lifetime is in a sufficient level for 2.5-10 Gbit/s high-speed LAN and data-link applications.

Vertical cavity surface emitting lasers (VCSELs) for optical interconnections operating at 1.07 mum have been developed. Active layers of the devices are InGaAs/GaAs MQWs, which are suitable for high-speed operation and high reliability. The devices exhibit -3 dB modulation bandwidths up to 19 GHz and no degradation under 70degC 1000 hour APC tests

This paper reports on the performance of the four-wavelength 10-Gb/s GaInNAs VCSELs for a 40-Gb/s CWDM system. WDM transmission characteristics using a optical multiplexer and a demultiplexer including dielectric thin film filters is also demonstrated.

In this paper, we will report the performance of a high-sensitivity (-28.7 dB) avalanche photodiode (APD) receiver, constructed with a low-noise superlattice APD, for l0-Gb/s applications. This receiver sensitivity value is only about 4-5 dB away from that of a commercially realizable optical pre-amplifier receiver at this bit-rate. Using this receiver and a transmitter with an output optical power of only -4 dB, we are able to transmit data over 61 km of standard fiber, including system operational margins, without using any optical amplifiers.

Reliability tests of mesa-structure InAlGaAs-InAlAs superlattice avalanche photodiodes (SL-APDs) have been performed by accelerated aging at three different temperatures for the first time. The lifetime of the SL-APDs is estimated to be over 1.0/spl times/10/sup 5/ hours at 50/spl deg/C with a degradation activation energy of 1 eV. These results indicate that the SL-APDs have a reliable lifetime for 2.5-10 Gb/s LAN applications.

High-speed quasi-planar-structure InAlGaAs-InAlAs superlattice avalanche photodiodes (SL-APDs) have been fabricated with a newly proposed Ti-implanted guard-ring. The APDs exhibited a uniform multiplication profile at a multiplication factor of 50 with no edge-multiplication. The dark current was 2.2 /spl mu/A at a multiplication factor of 10. High-speed response characteristics were confirmed with a gain-bandwidth product of 110 GHz and a high cut-off frequency of 15 GHz, even at a low multiplication factor of 1.5. These characteristics are the first demonstration of planar-structure SL-APDs for 10 Gb/s optical receivers use.

GaAs pin-photodiodes (PIN-PDs) with a wide bandgap AlGaInP window layer were demonstrated for a graded-index plastic optical fiber (GI-POF) data link at a wavelength of 650 nm as a high-speed and low-bias operation receiver. High quantum efficiency of over 80% was obtained in the wavelength range from 600 to 850 nm. A 3-dB bandwidth of 4.3 GHz was achieved in 90 /spl mu/m/spl phi/ PIN-PDs. High speed operation up to 600 Mb/s in 210 /spl mu/m/spl phi/ PIN-PDs was demonstrated under the bias free condition.