Stereolithography Cure Process Modeling Using Acrylate Resin

In this paper, a complex stereolithography (SL) cure process model is presented that incorporates transient thermal and chemical effects which influence final part shape and properties. The model incorporates photopolymerization, mass diffusion, and heat transfer. Material properties are characterized and a comprehensive kinetic model parameterized for a model compound system. SL process simulations are performed using finite element methods with the software package FEMLAB, and validated by the capability of predicting the fabricated part dimensions. A degree of cure (DOC) threshold model is proposed which can predict the cure line size within 15% error, comparing with 30% prediction error by the exposure threshold model currently used in SL. Furthermore, through the sensitivity analysis conducted by the process model presented here, the sensitive parameters are identified and the SL bath temperature, photointiator absorptivity and concentration are found to be the most sensitive factors that affect the SL fabrication results. The sensitive variables will be the focus of further research meant to improve SL process speed and resolution.Mechanical Engineerin

Is the US Population Behaving Healthier?

In the past few decades, some measures of population risk have improved, while others have deteriorated. Understanding the health of the population requires integrating these different trends. We compare the risk factor profile of the population in the early 1970s with that of the population in the early 2000s and consider the impact of a continuation of recent trends. Despite substantial increases in obesity in the past three decades, the overall population risk profile is healthier now than it was formerly. For the population aged 25-74, the 10 year probability of death fell from 9.8 percent in 1971-75 to 8.4 percent in 1999-2002. Among the population aged 55-74, the 10 year risk of death fell from 25.7 percent to 21.7 percent. The largest contributors to these changes were the reduction in smoking and better control of blood pressure. Increased obesity increased risk, but not by as large a quantitative amount. In the future, however, increased obesity may play a larger role than continued reductions in smoking. We estimate that a continuation of trends over the past three decades to the next three decades might offset about a third of the behavioral improvements witnessed in recent years.

Factors associated with voluntary HIV testing and serostatus among North Carolina state prisoners, 2004-2006

Background. Despite the heavy burden of HIV among prisoners, HIV testing strategies vary widely across US state prison systems. A voluntary HIV testing program in a large southern state prison system was evaluated by estimating HIV testing rates among prisoners, identifying inmate characteristics associated with testing status and infection status, and estimating the number of infected prisoners who remained untested during their incarceration. Methods. Electronic imprisonment and lab records were obtained for all prisoners entering the NC DOC between January 2004 and May 2006. Associations between inmate characteristics and both HIV testing and HIV serostatus were estimated separately using loglinear and logistic regression. The number of undetected cases was estimated using age-sexrace specific HIV prevalences from tested prisoners and from statewide HIV reporting. Results. Eight-five percent of female and 31% of male prisoners were tested for HIV during their incarceration. In four of the six intake prisons for men, 60% of men reporting a conventional risk behavior remained untested. In bivariate and covariate-adjusted analyses, black men were 30% and 13%, respectively, less likely than whites to be tested. Nearly 3.4% (718/21,419) of tested prisoners were HIV+. Of those HIV+ prisoners, <50% reported a history of any conventional HIV risk behaviors. Infection was most strongly associated with being a MSM (OR=8.0), non-white race (OR=6.2-7.4), and ages 35- 44 years (OR=4.1). The strongest risk factor among women was black race (OR=3.8); ORs < 3.0 were observed for several other risk factors. Sixty-five percent of HIV+ prisoners were HCV-coinfected. Between 23% and 63% of HIV cases remained undetected. Conclusion. HIV testing varied greatly by intake prison, and many male inmates were never tested. The majority of cases denied conventional HIV risk behaviors suggesting limitations of risk-factor based testing. Expanded HIV testing could improve case finding. However, testing expansion must be joined with adequate treatment and follow-up services, and monitoring is needed to ensure testing is not coercive

Jail Health and Early Release Practices

Local jails in the United States incarcerate millions of people each year. The COVID-19 pandemic made jail health a pressing public health concern nationally, where releasing individuals from jails occurred across the country in order to prevent pandemic spread. But releases also faced substantial resistance and exposed long-standing challenges in delivering adequate healthcare in jail settings. People in jail have substantially higher levels of medical need than individuals in the general population, with large numbers having serious mental illnesses and substance use disorders. Further, overcrowded conditions and poor healthcare standards and delivery make jails harmful to those already-vulnerable people. What means exist to protect individuals whose health would suffer in jail? Constitutional standards under the Eighth Amendment are highly deferential to jail administrators, nor is there substantial state or local level regulation of jail health. However, more informal mechanisms do exist, and they may be more responsive to health-based needs than constitutional or legal rights. This Article describes insights from qualitative interviews with jail medical staff in four states, to explore what challenges face delivery of healthcare, but more specifically, when health-based needs require counsel releasing individuals from jail. The Article describes widespread informal and unwritten mechanisms for health-based releases from jails. The Article will present the data and how such practices have implications for reforming the legal rules surrounding jail healthcare

Propulsion simulation for magnetically suspended wind tunnel models

The feasibility of simulating propulsion-induced aerodynamic effects on scaled aircraft models in wind tunnels employing Magnetic Suspension and Balance Systems. The investigation concerned itself with techniques of generating exhaust jets of appropriate characteristics. The objectives were to: (1) define thrust and mass flow requirements of jets; (2) evaluate techniques for generating propulsive gas within volume limitations imposed by magnetically-suspended models; (3) conduct simple diagnostic experiments for techniques involving new concepts; and (4) recommend experiments for demonstration of propulsion simulation techniques. Various techniques of generating exhaust jets of appropriate characteristics were evaluated on scaled aircraft models in wind tunnels with MSBS. Four concepts of remotely-operated propulsion simulators were examined. Three conceptual designs involving innovative adaptation of convenient technologies (compressed gas cylinders, liquid, and solid propellants) were developed. The fourth innovative concept, namely, the laser-assisted thruster, which can potentially simulate both inlet and exhaust flows, was found to require very high power levels for small thrust levels

Functional correlates of optic flow motion processing in Parkinson’s disease

The visual input created by the relative motion between an individual and the environment, also called optic flow, influences the sense of self-motion, postural orientation, veering of gait, and visuospatial cognition. An optic flow network comprising visual motion areas V6, V3A, and MT+, as well as visuo-vestibular areas including posterior insula vestibular cortex (PIVC) and cingulate sulcus visual area (CSv), has been described as uniquely selective for parsing egomotion depth cues in humans. Individuals with Parkinson’s disease (PD) have known behavioral deficits in optic flow perception and visuospatial cognition compared to age- and education-matched control adults (MC). The present study used functional magnetic resonance imaging (fMRI) to investigate neural correlates related to impaired optic flow perception in PD. We conducted fMRI on 40 non-demented participants (23 PD and 17 MC) during passive viewing of simulated optic flow motion and random motion. We hypothesized that compared to the MC group, PD participants would show abnormal neural activity in regions comprising this optic flow network. MC participants showed robust activation across all regions in the optic flow network, consistent with studies in young adults, suggesting intact optic flow perception at the neural level in healthy aging. PD participants showed diminished activity compared to MC particularly within visual motion area MT+ and the visuo-vestibular region CSv. Further, activation in visuo-vestibular region CSv was associated with disease severity. These findings suggest that behavioral reports of impaired optic flow perception and visuospatial performance may be a result of impaired neural processing within visual motion and visuo-vestibular regions in PD.Published versio

Papapetrou Energy-Momentum Tensor for Chern-Simons Modified Gravity

We construct a conserved, symmetric energy-momentum (pseudo-)tensor for Chern-Simons modified gravity, thus demonstrating that the theory is Lorentz invariant. The tensor is discussed in relation to other gravitational energy-momentum tensors and analyzed for the Schwarzschild, Reissner-Nordstrom, and FRW solutions. To our knowledge this is the first confirmation that the Reissner-Nordstrom and FRW metrics are solutions of the modified theory.Comment: 8 pages; typos corrected, references fixed, some calculations shortene

In vitro variability in fentanyl absorption by different membrane oxygenators

The membrane oxygenator has replaced the bubble oxygenator in a wide variety of clinical settings. The membrane oxygenators now manufactured can be grouped into three categories based on composition and design: (1) silicone with a true membrane structure; (2) polypropylene with a microporous sheet; and (3) polypropylene with a microtubular structure. The capacity for fentanyl uptake by membrane oxygenators from these three categories was studied in vitro. Representative membrane samples were incubated in solutions containing tritiated fentanyl in Normosol-R (Abbott, North Chicago, IL) with pH adjusted to 7.4 at 37[deg]C. Fentanyl analysis was performed using liquid scintillation and radioimmunoassay techniques. The uptake of fentanyl at various concentrations (340 to 10 ng/mL) was studied. The SciMed (type 1: SciMed, Minneapolis, MN) membrane showed the greatest capacity for fentanyl uptake at all concentrations. The SciMed oxygenator was capable of binding 130 ng fentanyl/cm2 membrane. When presented with a smaller concentration (2, respectively. Using the higher fentanyl concentrations (2 compared with only 2 ng/cm2 by the Shiley. The Bentley BCM 7 and Terumo Capiox 1108 microtubular microporous membranes (type 3) did not show absorption of fentanyl using isolated or intact membrane models. It is concluded that oxygenators of different design and/or composition have different capacities for fentanyl uptake.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28547/1/0000346.pd