[Cut-off point of the risk assessment scale for the 9-year risk of functional disability].

Objectives　This study aimed to examine the cut-off point of the Risk Assessment Scale (RAS) for predicting the 9-year risk of functional disability among older Japanese adults.Methods　This prospective, 9-year follow-up study used data from the Sasaguri Genkimon Study in Fukuoka. Of the 2,629 older adults who did not have functional disabilities and participated in the baseline survey in 2011, 2,254 with complete data were included in the analysis. The RAS was assessed using a questionnaire that showed good predictive and external validity for the 3-year risk of functional disability. The outcome was the incidence of functional disability during follow-up, which was defined as a new certification for the need for support or care. The cut-off point of the RAS was estimated as the point indicating the maximum χ2 value of the log-rank test. The predictive validity of the RAS for functional disability was examined using C-statistics for the total score, and sensitivity and specificity for the cut-off point, respectively. Participants were then categorized into two groups according to the cut-off point (high-score and low-score groups). Hazard ratio (HR) and 95% confidence interval (95% CI) of the 9-year risk of functional disability for the high-score group compared with the low-score group were calculated using the Cox proportional hazard model. In the multivariate model, HR was adjusted for living alone, education, economic status, drinking, smoking, and multimorbidity.Results　New functional disability was certified in 647 participants (28.7%) during a median follow-up period of 8.75 years. The cut-off point for functional disability was 13/14. The C-statistic was 0.774, and the sensitivity and specificity were 0.726 and 0.712, respectively. Compared to the low-score group (0-13 points), the HR (95% CI) of the high-score group (≥ 14 points) for incident functional disability in 9 years was 5.50 (4.62-6.54) in the crude model, and 4.81 (4.00-5.78) in the multivariate model (P<.001).Conclusion　This study, with its long follow-up period of 9 years, demonstrated that the 13/14 cut-off point of the RAS is suitable for the long-term assessment of functional disability risk. Our results suggest the possibility of using the 13/14 cut-off point of the RAS as a promising tool to grasp the risk of functional disability over a longer time frame, highlighting the potential for early prevention and intervention.

Frailty and occupational falls among older Japanese workers: An Internet-based cross-sectional study.

OBJECTIVES: Occupational falls are a major problem for older workers, especially those in the tertiary industry. Recently, it has been suggested that frailty is associated with occupational falls, but it is unclear whether this holds true for older workers in the tertiary industry. This study examined the relationship between frailty and occupational falls among older workers in the tertiary industry. METHODS: This was an Internet-based cross-sectional study. We recruited 5000 older workers (age, 60-75 years) employed in the tertiary industry who were registered with an Internet research company. Frailty was assessed using the Frailty Screening Index's five items, and participants were classified into robust, pre-frailty, or frailty groups. Occupational falls were defined as falls experienced in the past 12 months while at work. The relationship between frailty and occupational falls was analyzed by logistic regression analysis. RESULTS: It was found that 6.1% of participants had experienced at least one occupational fall in the past 12 months. On the multivariate analysis, the adjusted odds ratio (aOR) for falls was higher with pre-frailty (aOR: 1.95, 95% confidence interval: 1.30-2.94, P = .001) and frailty (aOR: 4.26, 95% confidence interval: 2.74-6.65, P < .001) compared with robust. Similar results were obtained when the outcome was occupational falls with injury. CONCLUSION: Our findings suggest that frailty is associated with occupational falls among older workers in tertiary industries. We recommend that employers introduce frailty screening, and consider countermeasures based on the screening results to prevent occupational falls among older workers.

Analytical and Physical Investigation on Source Resistance in InxGa1-xAs Quantum-Well High-Electron-Mobility Transistors.

We present a fully analytical model and physical investigation on the source resistance (RS) in InxGa1-xAs quantum-well high-electron mobility transistors based on a three-layer TLM system. The RS model in this work was derived by solving the coupled quadratic differential equations for each current component with appropriate boundary conditions, requiring only six physical and geometrical parameters, including ohmic contact resistivity (ρc), barrier tunneling resistivity (ρbarrier), sheet resistances of the cap and channel regions (Rsh_cap and Rsh_ch), side-recessed length (Lside) and gate-to-source length (Lgs). To extract each model parameter, we fabricated two different TLM structures, such as cap-TLM and recessed-TLM. The developed RS model in this work was in excellent agreement with the RS values measured from the two TLM devices and previously reported short-Lg HEMT devices. The findings in this work revealed that barrier tunneling resistivity already played a critical role in reducing the value of RS in state-of-the-art HEMTs. Unless the barrier tunneling resistivity is reduced considerably, innovative engineering on the ohmic contact characteristics and gate-to-source spacing would only marginally improve the device performance.

Changes of Oral and Physical Functions in Older Japanese Who Participated in Keyboard Harmonica and Exercise Classes during COVID-19-Related Movement Restrictions.

Many older people have restricted activities or movements because of the coronavirus disease 2019 (COVID-19) pandemic, which causes concerns about secondary health problems. This study aimed to investigate how frailty-prevention activities implemented by local governments have changed the health of community-dwelling older people during the COVID-19 pandemic. In this observational study, the participants were 23 older Japanese people who took part in keyboard harmonica or exercise classes in 2021. Oral function examination and physical function tests were conducted at baseline and after 10 months of follow-up. In each class, the participants met 15 times and worked on assignments at home. The results showed that oral diadochokinesis/pa/, which represents lip dexterity, improved during 10 months (from 6.6 to 6.8 times/s, p < 0.046); however, grip strength (p < 0.005) and total skeletal muscle mass (p < 0.017) decreased in the keyboard harmonica group. In the exercise group, a statistically significant difference was found only in grip strength, which decreased (p < 0.003). The oral and physical functions of older people who participated in frailty-prevention activities implemented by local governments characteristically changed. Moreover, activity restrictions during the COVID-19 pandemic may have caused decreased grip strength.

Explicit Thermal Resistance Model of Self-Heating Effects of AlGaN/GaN HEMTs with Linear and Non-Linear Thermal Conductivity.

We presented an explicit empirical model of the thermal resistance of AlGaN/GaN high-electron-mobility transistors on three distinct substrates, including sapphire, SiC, and Si. This model considered both a linear and non-linear thermal resistance model of AlGaN/GaN HEMT, the thickness of the host substrate layers, and the gate length and width. The non-linear nature of channel temperature-visible at the high-power dissipation stage-along with linear dependency, was constructed within a single equation. Comparisons with the channel temperature measurement procedure (DC) and charge-control-based device modeling were performed to verify the model's validity, and the results were in favorable agreement with the observed model data, with only a 1.5% error rate compared to the measurement data. An agile expression for the channel temperature is also important for designing power devices and monolithic microwave integrated circuits. The suggested approach provides several techniques for investigation that could otherwise be impractical or unattainable when utilizing time-consuming numerical simulations.

Predictive ability of the total score of the Kihon checklist for the incidence of functional disability in older Japanese adults: An 8-year prospective study.

AIM: To investigate the association between the total score of the Kihon checklist (t-KCL score) and functional disability over an 8-year follow-up period, and to examine whether the t-KCL score in the basic model with risk factors contributes to the incremental predictive ability for functional disability among older adults. METHODS: We followed 2209 older adults aged ≥65 years without functional disability at baseline. The t-KCL score was determined using a baseline survey questionnaire. Functional disability was defined based on information from long-term care certifications. The association between the t-KCL score and functional disability was examined using the Cox proportional hazards model. The incremental predictive ability of the t-KCL score for functional disability was evaluated by the difference of the C-statistic, category-free net reclassification improvement (NRI), and integrated discrimination improvement (IDI). RESULTS: The median follow-up period was 7.8 years, and 557 participants developed functional disability. The adjusted hazard ratio (95% confidence interval [CI]) of functional disability for a 1-point increase of the t-KCL score was 1.08 (1.06-1.10). Adding the t-KCL score to the basic model significantly improved the C-statistic (95% CI) from 0.747 (0.728-0.768) to 0.760 (0.741-0.781). When the t-KCL score was added to the basic model, the NRI and IDI were 0.187 (95% CI: 0.095-0.287) and 0.020 (95% CI: 0.012-0.027), respectively. CONCLUSIONS: The t-KCL score had an independent positive association with functional disability over an 8-year follow-up. Furthermore, adding the t-KCL score to the basic model improved the predictive ability for functional disability. Geriatr Gerontol Int 2022; 22: 723-729.

224-Gbit/s 4-PAM operation of a high-modulation-bandwidth high-output-power Hi-FIT AXEL transmitter.

We fabricated an optical transmitter with high frequency and integrated design based on the flip-chip interconnection technique (Hi-FIT) and assisted extended reach electroadsorption modulator integrated distributed feedback (EADFB) laser (AXEL) for 200-Gbit/s/λ application. The Hi-FIT makes it possible to increase modulation bandwidth thanks to wire-free interconnection and peaking control techniques while the AXEL can increase the optical modulation output power thanks to an integrated semiconductor optical amplifier (SOA). The fabricated Hi-FIT AXEL transmitter has a 3-dB bandwidth of more than 66 GHz. We obtained clear 224-Gbit/s 4-level pulse amplitude modulation (4-PAM) eye diagrams with a chip-output optical modulation amplitude (OMA) of more than +7.9 dBm at distributed feedback (DFB) laser and SOA currents of 70 and 30 mA, respectively.

A quantitative approach for trap analysis between Al0.25Ga0.75N and GaN in high electron mobility transistors.

The characteristics of traps between the Al0.25Ga0.75N barrier and the GaN channel layer in a high-electron-mobility-transistors (HEMTs) were investigated. The interface traps at the Al0.25Ga0.75N/GaN interface as well as the border traps were experimentally analyzed because the Al0.25Ga0.75N barrier layer functions as a dielectric owing to its high dielectric constant. The interface trap density Dit and border trap density Nbt were extracted from a long-channel field-effect transistor (FET), conventionally known as a FATFET structure, via frequency-dependent capacitance-voltage (C-V) and conductance-voltage (G-V) measurements. The minimum Dit value extracted by the conventional conductance method was 2.5 × 1012 cm-2·eV-1, which agreed well with the actual transistor subthreshold swing of around 142 mV·dec-1. The border trap density Nbt was also extracted from the frequency-dependent C-V characteristics using the distributed circuit model, and the extracted value was 1.5 × 1019 cm-3·eV-1. Low-frequency (1/f) noise measurement provided a clearer picture of the trapping-detrapping phenomena in the Al0.25Ga0.75N layer. The value of the border trap density extracted using the carrier-number-fluctuation (CNF) model was 1.3 × 1019 cm-3·eV-1, which is of a similar level to the extracted value from the distributed circuit model.

Quasi-continuous tuning of a 1.3-µm-wavelength superstructure grating distributed Bragg reflector laser by enhancing carrier-induced refractive index change.

To overcome the limitation of the small tuning range of 1.3-µm-wavelength distributed Bragg reflector (DBR) lasers using the carrier-plasma effect, we designed a DBR structure with InAlAs carrier confinement layers and an InGaAlAs core layer. We found that the enhanced carrier density and small effective mass of electrons in the core layer of the DBR regions resulted in a wide Bragg wavelength shift. The enhanced refractive-index change due to the new structure enabled us to fabricate the world's first 1.3-µm-wavelength superstructure-grating DBR laser with a quasi-continuous tuning range of over 30 nm.

Linearity improvement of high-speed avalanche photodiodes using thin depleted absorber operating with higher order modulation format.

We present an avalanche photodiode (APD) with high-speed, high-responsivity and high-linearity operation to cope with higher order modulation format, such as pulse-amplitude modulation (PAM). A hybrid absorber configuration with thin depleted region which we newly employed successfully eliminates the space charge effect in the APD while maintaining high responsivity and operating speed. The fabricated APD shows an improved optical-input-electrical-output linearity for an optical input power over -8 dBm, and an optical receiver with this APD achieves both an error-free operation with a KP4 FEC and a high sensitivity of -17 dBm against a 28-Gbaud PAM4 signal.

50-Gbit/s vertical illumination avalanche photodiode for 400-Gbit/s Ethernet systems.

50-Gbit/s error-free operation is demonstrated by a high-speed avalanche photodiode for the first time. The APD exhibits 3-dB bandwidth of 35 GHz and excellent receiver sensitivity of -10.8 dBm at a BER of 10(-12) against non-return to zero input optical signals. These results indicate our APD is promising for the systems with serial baud rate of 50 Gbit/s such as 400-Gbit/s Ethernet systems.

25-Gbit/s burst-mode optical receiver using high-speed avalanche photodiode for 100-Gbit/s optical packet switching.

25-Gbit/s error-free operation of an optical receiver is successfully demonstrated against burst-mode optical input signals without preambles. The receiver, with a high-sensitivity avalanche photodiode and burst-mode transimpedance amplifier, exhibits sufficient receiver sensitivity and an extremely quick response suitable for burst-mode operation in 100-Gbit/s optical packet switching.