Computation lithography: virtual reality and virtual virtuality.

Computation lithography is enabled by a combination of physical understanding, mathematical abstraction, and implementation simplification. An application in the virtual world of computation lithography can be a virtual reality or a virtual virtuality depending on its engineering sensibleness and technical feasibility. Examples under consideration include design-for-manufacturability and inverse lithography.

Initialization for robust inverse synthesis of phase-shifting masks in optical projection lithography.

The continuous shrinkage of minimum feature size in integrated circuit (IC) fabrication incurs more and more serious distortion in the optical projection lithography process, generating circuit patterns that deviate significantly from the desired ones. Conventional resolution enhancement techniques (RETs) are facing critical challenges in compensating such increasingly severe distortion. In this paper, we adopt the approach of inverse lithography in the mask design, which is a branch of design methodology to treat it as an inverse mathematical problem. We focus on using pixel-based algorithms to design alternating phase-shifting masks with minimally distorted output, with the goal that the patterns generated should have high contrast and low dose sensitivity. This is achieved with a dynamic-programming-based initialization scheme to pre-assign phases to the layout when alternating phase-shifting masks are used. Pattern fidelity and worst case slopes are shown to improve with this initialization scheme, which are important for robustness considerations.

Depressive Symptoms and Orthostatic Hypotension Are Risk Factors for Unexplained Falls in Community-Living Older People.

OBJECTIVES: To investigate risk factors for unexplained falls in older community-dwelling individuals. DESIGN: Prospective cohort study. SETTING: Community population, Sydney, Australia. PARTICIPANTS: Older adults (N = 529; mean age 79.8 ± 4.4, 52.2% female). MEASUREMENTS: Participants provided information demographic, medical, and medication characteristics and completed cardiovascular (tilt table test, pulse wave velocity), cognitive, and sensorimotor assessments at baseline. Falls were then recorded in monthly fall diaries for 12 months. Unexplained fallers (UFs) were those who reported falls due to a blackout, dizziness, feeling faint, or "found themselves suddenly on the ground." RESULTS: Of the 523 participants available at follow-up, 238 (45.5%) reported one or more falls; 35 participants fulfilled the definition of UFs. UFs were more likely than balance-related fallers (BFs) (n = 203) and nonfallers (n = 291) to have orthostatic hypotension (39.4%, 20.5% and 22.4%, respectively) and depressive symptoms (24.2%, 10.1%, and 7.9% respectively). More UFs (88.6%) than BFs (70.9%) had injurious falls. A multivariate logistic regression model revealed that depressive symptoms and orthostatic hypotension were significant and independent determinants of UF status. CONCLUSION: Approximately 15% of fallers had unexplained falls, which were more likely to result in injuries. Depressive symptoms and orthostatic hypotension increased the risk of unexplained falls, whereas cognitive deficits and sensorimotor and balance impairments did not. Future research should investigate whether psychotherapy and physical exercise to improve mood and medication reviews and nonpharmacological therapies for the treatment of orthostatic hypotension and depression are effective at reducing the risk of unexplained falls in older people.

High arterial pulse wave velocity is a risk factor for falls in community-dwelling older people.

OBJECTIVES: To examine whether arterial stiffness is a risk factor for falls in community-dwelling older people. DESIGN: Prospective cohort study. SETTING: Community population, Sydney, Australia. PARTICIPANTS: Community-dwelling older adults (mean age 79.8±4.4, 52.2% female; N=481). MEASUREMENTS: Carotid-femoral pulse wave velocity (PWV) was measured in the supine position after lying for 10 minutes. Demographic, medical, and medication characteristics and levels of physical activity were obtained in clinical interviews and questionnaires, and falls were recorded with monthly falls diaries for 12 months. RESULTS: Participants in the top quintile of PWV (high PWV) were more likely to have higher seated systolic blood pressure (SBP) and heart rate, unsatisfactory control of blood pressure, diabetes mellitus, and lower physical activity levels. These participants were also more likely to be male and taking cardiovascular medications. Of the 473 participants available for follow-up, 212 (44.8%) reported one or more falls. In modified Poisson regression analyses, high PWV was a risk factor for falls (relative risk=1.37, 95% confidence interval=1.06-1.78) after adjusting for use of psychotropic and cardiovascular medications, age, sex, body mass index, seated SBP, heart rate, and diabetes status. CONCLUSION: In community-dwelling older people, high PWV (as a measure of arterial stiffness) was a risk factor for falls after adjusting for potential demographic, anthropometric, disease, and medication confounders. Further research is required to investigate mediators for this association and the effect of lowering arterial stiffness on falls in older people.

Angiotensin system-blocking medications are associated with fewer falls over 12 months in community-dwelling older people.

OBJECTIVES: To investigate relationships between the use of cardiovascular medications, including angiotensin system-blocking medications (ASBMs), orthostatic hypotension (OH), fall risk, and falls in community-dwelling older people. DESIGN: Prospective cohort study. SETTING: Sydney, Australia. PARTICIPANTS: Five hundred twenty community-dwelling older adults. MEASUREMENTS: Medical, medication and falls history were obtained from a standardized questionnaire in all participants. Blood pressure was measured in supine, seated, and tilted positions. Fall risk was assessed using the Physiological Profile Assessment (PPA). Falls data were collected prospectively for 12 months using monthly fall calendars. Participants were defined as nonfallers (no falls) and fallers (≥ 1 falls) at the end of the 12-month follow-up. RESULTS: Participants taking medications affecting the angiotensin system had greater quadriceps strength, but after adjusting for sex, this difference became insignificant. People taking ASBMs were less likely to fall (odds ratio = 0.68, 95% confidence interval = 0.48-0.97), and the association between ASBMs and falls remained significant after adjusting for sex, body mass index, PPA score, and psychotropic medication and 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitor (statin) use. OH was more frequently observed in participants taking alpha adrenergic receptor blockers (α-blockers), but the presence of OH did not increase fall risk. CONCLUSION: The use of cardiovascular medications in older people did not increase the risk of falls, and the use of ASBMs was associated with lower fall risk. The mechanisms for this apparent protective effect are unclear and appear not to be directly related to muscle strength. More research is required to elucidate the possible protective effects of certain cardiovascular medications in relation to falls in older people.