Optimization of Aging Temperature and Heat-Treatment Pathways in Additively Manufactured 17-4PH Stainless Steel.

This study investigates the tensile behaviors of additively manufactured (AM) 17-4PH stainless steels heat-treated within various temperature ranges from 400 °C to 700 °C in order to identify the effective aging temperature. Despite an aging treatment of 400-460 °C increasing the retained austenite content, an enhancement of the tensile properties was achieved without a strength-ductility trade-off owing to precipitation hardening by the Cu particles. Due to the intricate evolution of the microstructure, aging treatments above 490 °C led to a loss in yield strength and ductility. A considerable rise in strength and a decrease in ductility were brought about by the increase in the fraction of precipitation-hardened martensitic matrix in aging treatments over 640 °C. The impact of heat-treatment pathways on aging effectiveness and tensile anisotropy was then examined. Direct aging at 482 °C for an hour had hardly any effect on wrought 17-4PH, but it increased the yield strength of AM counterparts from 436-457 to 588-604 MPa. A solid-solution treatment at 1038 °C for one hour resulted in a significant drop in the austenite fraction, which led to an increase in the yield (from 436-457 to 841-919 MPa) and tensile strengths (from 1106-1127 to 1254-1256 MPa) with a sacrifice in ductility. Improved strength and ductility were realized by a solid-solution followed by an aging treatment, achieving 1371-1399 MPa. The tensile behaviors of AM 17-4PH were isotropic both parallel and perpendicular to the building direction.

Unravelling thermal history during additive manufacturing of martensitic stainless steel.

In-situ thermal cycling neutron diffraction experiments were employed to unravel the effect of thermal history on the evolution of phase stability and internal stresses during the additive manufacturing (AM) process. While the fully-reversible martensite-austenite phase transformation was observed in the earlier thermal cycles where heating temperatures were higher than Af, the subsequent damped thermal cycles exhibited irreversible phase transformation forming reverted austenite. With increasing number of thermal cycles, the thermal stability of the retained austenite increased, which decreased the coefficient of thermal expansion. However, martensite revealed higher compressive residual stresses and lower dislocation density, indicating inhomogeneous distributions of the residual stresses and microstructures on the inside and on the surface of the AM component. The compressive residual stresses that acted on the martensite resulted preferentially from transformation strain and additionally from thermal misfit strain, and the decrease in the dislocation density might have been due to the strong recovery effect near the Ac1 temperature.

Reliability and Validity of the Korean Version of Clinician-Administered Posttraumatic Stress Disorder Scale for DSM-5.

BACKGROUND: For diagnosis of post-traumatic stress disorder (PTSD), the Clinician-Administered PTSD Scale (CAPS) is one of the most widely used structured diagnostic interviews. METHODS: In this study, we aimed to develop and validate the Korean version of CAPS for the Diagnostic and Statistical Manual of Mental Disorders, 5th edition ([DSM-5] K-CAPS-5). Seventy-one subjects with PTSD, 74 with mood disorder or anxiety disorder, and 99 as healthy controls were enrolled. The Korean version of the structured clinical interview for DSM-5-research version was used to assess the convergent validity of K-CAPS-5. BDI-II, BAI, IES-R, and STAI was used to evaluate the concurrent validity. RESULTS: All subjects completed various psychometric assessments including K-CAPS-5. K-CAPS-5 presented good internal consistency (Cronbach's α = 0.92) and test-retest reliability (r = 0.91). K-CAPS-5 showed strong correlations with the structured clinical interview for DSM-5 PTSD (k = 0.893). Among the three subject groups listed above there were significant differences in the K-CAPS-5 total score. The data were best explained by a six-factor model. CONCLUSION: These results demonstrated the good reliability and validity of K-CAPS-5 and its suitability for use as a simple but structured instrument for PTSD assessment.

Clinical utility of heart rate variability during Head-up tilt test in subjects with chronic posttraumatic stress disorder.

Posttraumatic stress disorder (PTSD) is characterized by psychophysiological abnormalities, such as an altered baseline heart rate and hyperarousal, implying dysfunctional arousal regulation. Heart rate variabilities (HRVs) is known to reflect autonomic nervous system activity. We examined the changes of HRVs in PTSD patients with head-up tilt position to closely investigate disease-specific changes in autonomic function in PTSD patients. Sixty-seven patients with PTSD and 72 patients without PTSD were assessed using the PTSD Checklist for DSM-5 (PCL-5) and psychiatric interview. Heart rate data including standard deviation of the NN intervals, the square root of the mean squared differences of successive NN intervals, log low-frequency and log high-frequency were collected for 10 min before and after tilting. Considering interactions between groups and head-up tilting, the head-up tilting induced reduction of the high-frequency component of HRVs was significantly greater in the PTSD group [F (1, 272) = 4.718, p = 0.031]. The change of HRVs in PTSD patients suggested the presence of autonomic dysfunction in despite of the posture.

Circadian Rhythm of Wrist Temperature among Shift Workers in South Korea: A Prospective Observational Study.

Background: Human body temperature varies with circadian rhythm. To determine the effect of shift work on the circadian rhythm of the distal-skin temperature, wrist temperatures were measured. Methods: Wrist-skin temperatures were measured by an iButton® Temperature Logger. It was measured every 3 min for two and eight consecutive working days in the day and shift workers, respectively. Mesor, amplitude, and acrophase were measured by Cosinor analysis. Results: The shift-worker amplitude dropped significantly as the night shift progressed (0.92 to 0.85 °C), dropped further during rest (0.69 °C), and rose during the morning-shift days (0.82 °C). Day workers still had higher amplitudes (0.93 °C) than the morning-shift workers. The acrophase was delayed during the four night-shift days, then advanced during rest days and the morning-shift days. Nevertheless, the morning-shift worker acrophase was still significantly delayed compared to the day workers (08:03 a.m. vs. 04:11 a.m.). Conclusions: The further reduction of wrist-temperature amplitude during rest after the night shift may be due to the signal circadian rhythm disruption. Reduced amplitudes have been reported to be associated with intolerance to shift work. The findings of our study may help to design the most desirable schedule for shift workers.

Heart rate variability of chronic posttraumatic stress disorder in the Korean veterans.

Patients with post-traumatic stress disorder (PTSD) have lower heart rate variability (HRV) than the general population, but findings in this area have been inconsistent. This study was conducted to investigate the characteristics of HRV in patients with PTSD and to evaluate associations between PTSD symptoms and HRV indices. Sixty-eight patients with PTSD and 73 controls without PTSD were evaluated. HRV was measured in all subjects after they completed self-reported questionnaires. Patients with PTSD had significantly more depressed moods, anxiety, and poorer sleep quality than individuals in the non-PTSD group. Standard deviations of NN intervals (SDNN), the square root of the mean squared differences of successive NN intervals (RMSSD), and log high-frequency (LNHF) were significantly lower in the PTSD group than in the non-PTSD group. Comparisons of HRV indices among four sub-groups according to presence/absence of PTSD and experiences of combat-related or other trauma indicated that individuals in the PTSD group who had experienced combat-related trauma had the lowest HRV indices. These indices included SDNN, RMSSD, and LNHF. Further, SDNN, RMSSD, and HF power were significantly associated with symptoms of hyperarousal. HRV measures might be useful physiological parameters in assessing and monitoring sympathovagal function in patients with PTSD.

Prevalence and clinical characteristics of insomnia and its subtypes in the Korean elderly.

BACKGROUND: Insomnia is known to be associated with psychiatric disorders, other sleep disorders and medical conditions, but the prevalence of insomnia diagnosis has never been estimated according to its subtypes. We studied the prevalence and clinical characteristics of insomnia diagnosis and its subtypes in the Korean elderly population. METHODS: Among 1423 sampled elderly individuals aged 60 years or older, 881 subjects participated in this study. The Athens Insomnia Scale was applied to detect insomnia symptoms, and insomnia diagnosis was finally evaluated using the international classification of sleep disorders, 2nd edition. To define insomnia subtypes, the DSM-IV-based interview, detailed history on sleep disorders and semi-structured interview for medical conditions were performed. Subsyndromal depression was defined when depressive symptoms did not meet the criteria for depressive disorders. RESULTS: The prevalence of insomnia disorder was 32.8% in all subjects, with the prevalence being significantly higher in women than in men (37.9% vs. 25.2%; p<0.001). The prevalence of insomnia subtypes was as follows; psychophysiological insomnia (PI), 20.5%; insomnia due to mental disorder 7.2%; insomnia due to general medical conditions 2.9%; insomnia in other sleep disorders 2.2%, and insomnia due to substance use 0.2%. Among subjects with PI, subsyndromal depression was diagnosed in 53.7%. CONCLUSIONS: Nearly one third of Korean elderly individuals suffer from insomnia and insomnia patients showed diverse comorbid conditions, especially depressive symptoms. By establishing insomnia subtypes, we can plan to treat comorbid conditions as well as insomnia itself.

Subjective memory complaints in an elderly population with poor sleep quality.

OBJECTIVES: The association between sleep disturbances and cognitive decline in the elderly has been putative and controversial. We evaluated the relation between subjective sleep quality and cognitive function in the Korean elderly. METHOD: Among 459 community-dwelling subjects, 352 subjects without depression or neurologic disorders (mean age 68.2 ± 6.1) were analyzed in this study. All the participants completed the Korean version of the consortium to establish a registry for Alzheimer's disease neuropsychological battery (CERAD-KN) as an objective cognitive measure and subjective memory complaints questionnaire (SMCQ). Based on the Pittsburgh sleep quality index, two types of sleepers were defined: 'good sleepers' and 'poor sleepers'. RESULTS: There were 192 good sleepers (92 men) and 160 poor sleepers (51 men). Poor sleepers reported more depressive symptoms and more use of sleep medication, and showed higher SMCQ scores than good sleepers, but there was no difference in any assessments of CERAD-KN. In the regression analysis, depressive symptoms and subjective sleep quality were associated with subjective memory complaints (ß = 0.312, p < 0.001; ß = 0.163, p = 0.005). CONCLUSION: In the elderly without depression, poor sleep quality was associated with subjective memory complaints, but not with objective cognitive measures. As subjective memory complaints might develop into cognitive disorders, poor sleep quality in the elderly needs to be adequately controlled.

Application of Short Screening Tools for Post-Traumatic Stress Disorder in the Korean Elderly Population.

OBJECTIVE: Post-traumatic stress disorder (PTSD) is often missed or incorrectly diagnosed in primary care settings. Although brief screening instruments may be useful in detecting PTSD, an adequate validation study has not been conducted with older adults. This study aimed to evaluate the reliability and validity of the Korean version of the primary care PTSD screen (PC-PTSD) and single-item PTSD screener (SIPS) in elderly veterans. METHODS: The PC-PTSD and SIPS assessments were translated into Korean, with a back-translation to the original language to verify accuracy. Vietnamese war veterans [separated into a PTSD group (n=41) and a non-PTSD group (n=99)] participated in several psychometric assessments, including the Korean versions of the PC-PTSD (PC-PTSD-K), SIPS (SIPS-K), a structured clinical interview from the Diagnostic and Statistical Manual of Mental Disorders-IV(SCID), and PTSD checklist(PCL). RESULTS: The PC-PTSD-K showed high internal consistency (Cronbach α=0.76), and the test-retest reliability of the PC-PTSD-K and SIPS-K were also high (r=0.97 and r=0.91, respectively). A total score of 3 from the PC-PTSD-K yielded the highest diagnostic efficiency, with sensitivity and specificity values of 0.90 and 0.86, respectively. The 'bothered a lot' response level from the SIPS-K showed the highest diagnostic efficiency, with sensitivity and specificity values of 0.85 and 0.89, respectively. CONCLUSION: Our findings suggest that both PC-PTSD-K and SIPS-K have good psychometric properties with high validity and reliability for detecting PTSD symptoms in elderly Korean veterans. However, further research will be necessary to increase our understanding of PTSD characteristics in diverse groups with different types of trauma.

A Shear Strain Route Dependency of Martensite Formation in 316L Stainless Steel.

In this study, the effect of simple shearing on microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. Two different shear strain routes were obtained by twisting cylindrical specimens in the forward and backward directions. The strain-induced martensite phase was effectively obtained by alteration of the routes. Formation of the martensite phase clearly resulted in significant hardening of the steel. Grain-size reduction and strain-induced martensitic transformation within the deformed structures of the strained specimens were characterized by scanning electron microscopy - electron back-scattered diffraction, X-ray diffraction, and the TEM-ASTAR (transmission electron microscopy - analytical scanning transmission atomic resolution, automatic crystal orientation/phase mapping for TEM) system. Significant numbers of twin networks were formed by alteration of the shear strain routes, and the martensite phases were nucleated at the twin interfaces.

Impacts of comorbidities on the association between arterial stiffness and obstructive sleep apnea in the elderly.

BACKGROUND: Although the impact of obstructive sleep apnea (OSA) on cardiovascular risk is reasonably well established in middle-aged patients, the debate persists as to whether OSA also increases this risk in the elderly. Arterial stiffness has been used as an early independent predictor of cardiovascular risk. STUDY OBJECTIVES: We sought to determine whether OSA has significant effects on the arterial stiffness in the elderly population and evaluate the impact of comorbidities on the association between arterial stiffness and OSA. METHODS: We performed a cross-sectional study in a university hospital. Elderly participants (≥60 years) were invited to participate in our study between November 2010 and January 2013. OSA was diagnosed using gold standard polysomnography and arterial stiffness was assessed by brachial-ankle pulse wave velocity (baPWV), cardio-ankle vascular index (CAVI) and central systolic and diastolic blood pressure (cSBP and cDBP). The high-sensitivity C-reactive protein (hs-CRP) level was also measured. RESULTS: We found no significant association between the severity of OSA and the arterial stiffness-related parameters cSBP, cDBP, baPWV, CAVI and hs-CRP. However, in patients with no comorbid medical conditions or use of medications (n = 101), we showed a modest association between OSA and arterial stiffness-related parameters and hs-CRP. CONCLUSION: We conclude that OSA is associated with increased arterial stiffness in an otherwise healthy elderly population, although the association was obviated by comorbidities and medications perhaps due to ceiling effects.

The prevalence of and risk factors for sleep-disordered breathing in an elderly Korean population.

BACKGROUND: There are just a few epidemiological studies on sleep-disordered breathing (SDB) in the elderly, and the results are inconsistent. STUDY OBJECTIVES: We sought to investigate the prevalence of and risk factors for SDB in a representative elderly population with the use of attended nocturnal polysomnography (NPSG). METHODS: Among 6,959 individuals aged ≥ 60 years living in Yongin City, Korea, 696 subjects were selected using random sampling. All the subjects were invited to visit a hospital for NPSG, and SDB was defined as an apnea-hypopnea index ≥ 15. RESULTS: Of the 696 participants investigated, 348 participants completed the sleep study and clinical evaluation. SDB was observed in 127 of the 348 participants, and the prevalence of SDB was 36.5% (52.6% in males and 26.3% in females). A body mass index ≥ 25 was associated with SDB in both male and female subjects, particularly in males, whereas snoring was independently associated with SDB in female participants only. In male participants, SDB was a significant risk factor for hypertension (p = 0.025). CONCLUSIONS: SDB was found to be common among elderly Koreans, and it was more prevalent and severe in male than in female subjects. Health consequences of SDB in the elderly need to be further explored.

A quantitative evaluation of microstructure by electron back-scattered diffraction pattern quality variations.

Band contrast (BC) is a qualitative measure of electron back-scattered diffraction (EBSD), which is derived from the intensity of the Kikuchi bands. The BC is dependent upon several factors including scanning electron microscope measurement parameters, EBSD camera setup, and the specimen itself (lattice defect and grain orientation). In this study, the effective factors for BC variations and the feasibility of using BC variations for the quantification of microstructure evolutions have been investigated. In addition, the effects of the lattice defect and the grain orientation on the BC variations are studied. Next, a shear-deformed microstructure of 316L stainless steel, which contains nanosized grains and a large portion of twin boundaries, is revealed by BC map and histogram. Recovery and recrystallization of shear-deformed 316L stainless steel are displayed by BC variations during isothermal annealing at 700 and 800°C, respectively. It is observed that the BC turns bright as the shear-deformed crystal structure is recovered or recrystallized.

REM sleep behavior disorder in the Korean elderly population: prevalence and clinical characteristics.

STUDY OBJECTIVES: To examine the prevalence and clinical characteristics of REM sleep behavior disorder (RBD) and subclinical RBD in the Korean elderly population. DESIGN: A community-based Korean Longitudinal Study on Cognitive Aging and Dementia and time-synchronized video-polysomnography (vPSG) in a laboratory. SETTING: Sleep laboratory in a university hospital. PARTICIPANTS: 348 individuals aged 60 years or older. INTERVENTION: N/A. MEASUREMENTS AND RESULTS: Among 696 subjects who were invited to participate in a vPSG study, 348 completed the vPSG. RBD was diagnosed when subjects showed REM sleep without atonia (RSWA) in the vPSG, and had history of complex and vigorous behaviors during sleep or abnormal REM sleep behaviors in the vPSG. Subjects with RSWA but no abnormal REM sleep behaviors were diagnosed with subclinical RBD. Seven subjects (5 male, 2 female) had RBD, three of whom (1 male, 2 female) had Parkinson disease. Two subjects reported history of sleep-related injury. The crude prevalence of RBD and idiopathic RBD was 2.01% (95% confidence interval [CI] = 0.54% to 3.49%) and 1.15% (95% CI = 0.03% to 2.27%). An age and sex-adjusted prevalence estimate of RBD and idiopathic RBD in the Korean elderly was 2.01% and 1.34%. Eighteen subjects were diagnosed with subclinical RBD, and the prevalence of subclinical RBD was estimated to be 4.95%. CONCLUSIONS: RBD and subclinical RBD are not rare in the elderly in the community with abnormal REM sleep behaviors of RBD being mild to injurious and violent. The clinical significance and long-term progression of subclinical RBD needs to be further explored, given the prevalence and its possible relation to RBD.

The impact of sleep apnoea syndrome on nocturia according to age in men.

UNLABELLED: Study Type--Symptom prevalence (cohort) Level of Evidence 2b. What's known on the subject? and What does the study add? Sleep apnoea syndrome (SAS) can be a risk factor for nocturia, although whether the relationship between nocturia and SAS changes according to age remains to be addressed. SAS has a modest impact on nocturia frequency and the prevalence of pathological nocturia in young adults and middle-aged men. However, SAS may not be a risk factor for nocturia in the elderly, and age-related urinary diseases and voiding dysfunctions could over-ride the influence of SAS on nocturia in the elderly. OBJECTIVE: • To assess the association between nocturia and sleep apnoea syndrome (SAS) according to age, as well as to determine the factors related to nocturia. PATIENTS AND METHODS: • A total of 1757 men who had been referred to a sleep laboratory underwent polysomnography. • Nocturia frequency was assessed using a questionnaire, and pathological nocturia was defined as the need to void two or more times per night. • The Pittsburgh Sleep Quality Index (PSQI) and Beck Depression Inventory (BDI) were applied to all study subjects. RESULTS: • Nocturia frequency was significantly correlated with age (r = 0.405, P < 0.001) and the apnoea-hypopnoea index (AHI) (r = 0.065, P < 0.01). • In those men aged <65 years, significant correlations were found between nocturic frequency and age, AHI, BDI and PSQI. • Multiple regression analysis showed that age (ß = 0.303, P < 0.001), AHI (ß = 0.107 P < 0.001) and benign prostatic hypertrophy (BPH; ß = 0.069, P < 0.01) were associated with nocturia, and that the presence of pathological nocturia was predicted by BPH (odds ratio [OR], 2.77; P < 0.01), age (OR, 1.09; P < 0.001) and AHI (OR, 1.02; P < 0.001). • However, in men aged >65 years, nocturia frequency was significantly associated with BDI and PSQI, although no relationship was found between nocturia frequency and SAS parameters. • BPH was more frequently observed in elderly men with pathological nocturia than in those without pathological nocturia (OR, 2.18; P < 0.05). CONCLUSIONS: • In the elderly, SAS may not be a risk factor for nocturia. • Age-related urinary diseases and voiding dysfunction may over-ride the influence of SAS.

The correlation of plasma Aß42 levels, depressive symptoms, and cognitive function in the Korean elderly.

OBJECTIVES: This study aims to investigate whether plasma amyloid beta 1-42 (Aß42) levels are associated with depressive symptoms and/or cognitive function in community dwelling elderly. METHODS: Subjects were 123 participants of a population-based project designed to screen community dwelling elderly older than 65 years old in Gangwon Province, Korea, for the early detection of depression and dementia. Symptoms of depression were assessed using the SGDS-K (Short Geriatric Depression Scale-Korean version), and the MMSE-KC (Mini-Mental State Examination-Korean version) was used to assess cognitive function. Plasma Aß42 levels were measured with the human amyloid beta ELISA Kit. RESULTS: The elderly with depressive symptoms (SGDS-K score ≥ 8) had higher plasma Aß42 levels than those without depressive symptoms (SGDS-K score<8) (p<0.1). Plasma Aß42 levels were positively correlated with SGDS-K scores (p<0.05). However, MMSE-KC scores were inversely associated with plasma Aß42 levels (p<0.01). Plasma ß42 levels were also associated with MMSE-KC (F=8.07, p<0.01) and SGDS-K (F=4.53, p<0.05) by generalized linear model (GLM) with controlling age, sex and education. CONCLUSION: Plasma Aß42 levels were associated with depressive symptoms and cognitive function in community dwelling elderly. The present study supports the possibility that plasma Aß may be involved in the development of late onset depression.