Experimental Investigation of the Small-scale Fixed Multi-chamber OWC Device

Sea wave energy generators or converters (WECs) have the potential to become a viable technology for clean, renewable energy production. Among the WEC technologies, the oscillating water columns (OWCs) are the most common WEC devices studied. These have been studied and developed over many years. Multi-chamber oscillating water columns (MC-OWC) have the potential to have a higher energy conversion when extracting energy in mixed sea states than single-chamber devices. In the work reported in this paper, physical experiments are carried under regular wave conditions to test the wave power extraction of a fixed MC-OWC small-scale model. The Power Take-Off (PTO) of the device is simulated using orifice plates. The flow characteristics through these orifices are pre-calibrated such that the extracted power can be obtained only using the pressure measurement. Wave condition effects on the damping of the PTO of the device power extraction are addressed. The test results illustrate that the PTO system damping is critical and affects device performance.

1225Symptoms of depression and anxiety in Dutch adults during and before the COVID-19 pandemic

Background The COVID-19 pandemic may impact mental health outcomes differentially based on an inidivdual’s capital, i.e. resources used to maintain and enhance health. This study examined changes in depression and anxiety symptoms before and during the pandemic, and assessed their association with different elements of capital. Methods Data from 65,854 individuals (Mage=50.4, SDage=12.0) from the Lifelines COVID-19 cohort were used. Baseline mental health symptoms were on average measured 4.7 (SD = 1.1) years before the first COVID-19 measurement wave (T1), and subsequent waves were (bi)weekly (March 30 — August 05, 2020). Mental health symptom trajectories were estimated using a two-part Latent Class Growth Analysis (cutoff=2 symptoms), and class membership was predicted by several elements of economic (education, income, and occupation) and person capital (neuroticism). Results Most individuals were unlikely to report □2 symptoms of depression (80.6%) and anxiety (75.9%), but small stable-high classes for both conditions were identified (1.6% and 6.7%, respectively). Compared to T0, T1 showed increases in the mean number of symptoms (Mdep_t0=4.1 vs Mdep_t1=4.7, Manx_t0=4.2 vs Manx_t1=4.3) and probability of reporting symptoms (Probdep_t0=0.65 vs Probdep_t1=0.96, Probanx_t0=0.70 vs Probanx_t1=0.92). Lower income (ORdep=1.10; 95%CI:1.05-1.16; ORanx=1.05; 95%CI:1.02-1.07) and higher neuroticism (ORdep=1.10; 95%CI:1.09-1.11; ORanx=1.08; 95%CI:1.08-1.09) increased the odds of being in both stable-high classes. Low education increased the odds of being in the stable-high depression class (ORdep=1.46; 95%CI:1.07-1.99), and higher occupation increased the odds of being in the stable-high anxiety class (ORanx=1.06; 95%CI:1.03-1.09). Conclusion Overall, a minority of individuals, who generally possessed less capital, reported an increase in symptoms of depression or anxiety. Key message Inidividuals with less capital, i.e. resources, generally experienced more symptoms of depression and anxiety, which stresses the importance of devoting more resources to improve their mental health. Keywords Longitudinal studies, Social epidemiology/determinants, Mental health

Steeling or sensitizing? A longitudinal examination of how ongoing accumulation of negative life events affects depressive symptoms in older adults

Objectives To examine whether: 1) as people age, accumulation of negative events increases (‘sensitizing’) or decreases (‘steeling’) the detrimental effects of subsequent events on depressive symptoms, and 2) how particular psychosocial factors are associated with the strength of these steeling or sensitizing effects. Method We used data from six measurement waves from 2,069 adults aged 55-84 (M=68.0) at baseline in the Longitudinal Aging Study Amsterdam, the Netherlands. We included 18 different life events across the life course. Using hybrid multilevel models, we tested whether the effects of proximate life events (<3 years) on depressive symptoms (measured by the CES-D) were moderated by previous cumulative events (childhood until previous measurement wave). Additionally, we tested whether education, mastery, emotional support, neuroticism, having strong faith, and loneliness were associated with the strength of steeling/sensitizing effects. Results Cumulative and proximate life events were independently associated with more depressive symptoms. Interaction effects indicated that the more cumulative life events, the weaker the effects of recent life events, suggesting a ‘steeling’ effect. Unexpectedly, three-way interaction effects showed that higher mastery and lower neuroticism were associated with weaker steeling effects. These effects were predominantly attributable to within-person changes rather than to fixed between-person differences. Results from analyses with event severity scores were similar. Conclusions As a population, older adults appear to become more resilient against new stressors as they accumulate experience in dealing with negative life events. Findings on mastery tentatively suggest that accepting limits to one’s own control over life circumstances may foster a steeling effect.

Multi-Sensor Measurement of Physical Behavior in the Finnish Retirement and Aging Study

Retirement is a life transition that is accompanied by changes in time use and removal of work-related exposures. The Finnish Retirement and Aging study (FIREA) was established in 2013 to examine changes in 24-hour physical behavior, lifestyle factors, health and functioning by following aging workers annually from full-time work to retirement. FIREA activity substudy includes 1200 participants (mean age 63.2 years, 85% women) and their physical behavior has been measured annually with multiple accelerometers (wrist ActiGraph, thigh Axivity and hip SenseDoc including GPS). The mean number of measurement days is seven at each measurement wave with a valid wake wear time 16.0 hours before retirement and 15.6 hours after retirement. Currently, information is available from 3-5 measurement waves. Transition to retirement induced changes in 24-h physical behavior towards increased sleep and less physical activity among women, especially in those retiring from manual occupations.

Need fulfillment, need importance, and depressive symptoms of residents over the first eight months of living in a nursing home

ABSTRACTBackground:Based on self-determination theory and adaptation theories, the study aim was to investigate the relationship between need fulfillment (of autonomy, relatedness, and competence), need importance, and depressive symptoms during the first months of living in a nursing home.Methods:Eight-month longitudinal questionnaire study in which 75 persons newly admitted to units for physically frail residents participated at baseline. Twenty-three longitudinal participants were remaining at the third and final measurement wave.Results:The results show a main effect of need fulfillment and an interaction effect of need fulfillment and need importance on depressive symptoms over time. A prototypical plot shows that residents with low need fulfillment had higher initial levels of depressive symptoms that decreased modestly over time, regardless of their need importance. Residents with high need fulfillment had lower initial levels of depressive symptoms, but their trajectories differed for participants with low and high need importance. Residents with low need importance started with lower levels of depressive symptoms but remained stable over time, whereas residents with high need importance had more depressive symptoms at T1 that decreased slightly over time.Conclusions:In general, depressive symptoms do not change over time. However, individual trajectories of depressive symptoms seem to depend on individual need fulfillment and need importance. The residents that consider need fulfillment to be highly important but experience low need fulfillment had higher initial levels of depressive symptoms that decreased modestly over time, although the level of depressive symptoms remained higher as compared to the other residents.

Ocean Wave Measurement Using GPS Buoys

The observation of ocean wave parameters is necessary to improve forecasts of ocean wave conditions. In this paper, we investigate the viability of using a single GPS receiver to measure ocean-surface waves, and present a method to enhance the accuracy of the estimated wave parameters. The application of high-pass filtering to GPS data in conjunction with directional wave spectral theory is a core concept in this article. Laboratory experiments were conducted to test the viability and accuracy measurements of wave parameters made by a single GPS receiver buoy. These tests identified an error of less than 1% for the rotational arm measurement (wave height) and an error of 1% in verifications of the wave direction and wave period, and showed a 0.488 s bias; this is sufficiently accurate for many specific purposes. These results are based on the best cut-off frequency value derived in this study. A moored-sea GPS buoy on the Taiwanese coast was used to estimate the GPS-derived wave parameters. Our results indicate that data from a single GPS receiver, processed with the presented method to reduce the error of the estimated parameters, can provide measurements of ocean surface wave to reasonable accuracy.