112 research outputs found
Non-Management Director Options, Board Characteristics, and Future Firm Investments and Performance
This paper examines if non-management director pay packages are set in ways consistent with the optimal contracting theory. Under this theory, directors issue stock option grants as a means for providing non-management directors incentives to monitor adequately the risk-taking and investment opportunities that managers of the firm undertake. Our results are consistent with this theory. Using a sample of over 5,200 observations between 1997 and 2002, we find that (1) agency costs differ substantially across our sample, (2) boards systematically set their compensation contracts to address these agency costs, and (3) significantly positive links exist between the ratio of current stock option grants-to-total compensation and seven future investment, risk and firm performance variables. The investment variables are next period's change in research and development expenditures and change in capital expenditures. The risk variable is next year's stock return volatility. The firm performance variables are next period's Tobin's Q ratio, return on assets (ROA), a market return on current investments, and this period's stock return. Our results are incremental to board characteristics, CEO stock option grants, and economic, firm-specific, yearly, and industry control factors
Co-Evolution of Product Families and Assembly Systems.
To remain competitive in the midst of global competition and rapidly changing consumer tastes, manufacturers increased the amount of product variety they offer to the market and their responsiveness to changing market needs. Product families and reconfigurable manufacturing systems (RMS) enable manufacturers to cost effectively supply high product variety and to be responsive. However, there is a lack of systematic methods for the joint design of product families and RMSs.
Co-evolution of product families and assembly systems is introduced as a new method for the joint design and reconfiguration of product families and assembly systems within and across product generations. There are two main phases in the co-evolution methodology. The first phase involves the joint design of a product family and assembly system in the first generation. The second phase involves the joint evolution of the product family and assembly system between product generations.
For co-evolution, models are required for: (i) the joint design of a product family and its corresponding assembly system, (ii) the evolution of the product family within the constraints of an assisting assembly system, and (iii) the reconfiguration of the assembly system. Methodologies are introduced for the first and third problems in this dissertation.
Two non-linear integer programming (INLP) formulations are developed for the problem of the concurrent design of a single generation of a product family and assembly system. The objective of the first formulation is to maximize the efficiency of the assembly system and minimize the oversupply of functionality. The objective of the second formulation is to maximize profits. Genetic algorithms are introduced for the solution of these problems.
The assembly system reconfiguration planning (ASRP) problem is also formulated as INLP. Genetic algorithm and dynamic programming procedures are introduced for the solution of this problem. In addition, an algorithm for generating all the possible assembly system configurations is introduced.
Examples are used to demonstrate how the methods for co-evolution introduced in this dissertation can lead to reduced costs and increased responsiveness to market changes.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/60824/1/abryan_1.pd
Health Literacy and Occupational Therapy: A Discussion on Assessing and Addressing Limited Health Literacy
Health literacy is multidimensional and goes beyond simply education level. In addition, age, gender, race and ethnicity, social network, and income level, among other things, can contribute to the level of health literacy and affect health outcomes. Many Americans cannot make sound decisions regarding their health care because of limited health literacy, yet health literacy is rarely considered during an occupational therapy evaluation and subsequent plan of care. This manuscript informs occupational therapists on strategies to address limited health literacy by using literature and evidence
Volumetric Flank Wear Characterization for Titanium Milling Insert Tools
Machining wear models are useful for the prediction of tool life and the estimation of machining productivity. Existing wear models relate the cutting parameters of feed, speed, and depth of cut to tool wear. The tool wear is often reported as changes in flank width or crater depth. However, these one-dimensional wear measurements do not fully characterize the tool condition when tools wear by other types of wear such as notching, chipping, and adhesion. This is especially true when machining difficult-to-machine materials such as titanium. This paper proposes another approach for characterizing tool wear. It is based on taking measurements of the retained volume of the cutting tool. The new wear characterization approach is used to demonstrate the progression of volumetric wear in titanium milling
Spatial and Seasonal Nutrient Trends in Manila Bay Aquaculture Farms
Sampling was done in duplicates during dry (May 2014 and February 2015) and wet season (September 2014 and November 2014) following the blocking scheme for the nutrient trends. As for the nutrient loading, water samples were collected in three ponds after flooding (water intrusion) and prior to draining (water release). Colorimetric analyses by UV-Vis Spectroscopy following the US EPA standard methods were used to determine the samples’ nutrient levels specifically, ammonia, nitrate, nitrite, and phosphorus. Results showed that ammonia had the highest levels followed by phosphorus, nitrate, and nitrite. Geographically, higher concentration of nitrogen and phosphorus were observed in Eastern Bulacan aquaculture farms, which is attributed to the farmers’ disregard of the important pond preparation activities. Varying seasonal trends were noted among nutrient species due to the different reactions of each analyte under changing climatic conditions. Nutrient levels in sediments were several folds higher than that in the water column. Results of correlation analyses of nutrients in water and sediments showed: a) a good correlation for phosphorus, b) weak correlation for ammonia, and c) no correlation for nitrites and nitrates, implying that sediments maybe a possible contributor of phosphorus and ammonia in water but not nitrite and nitrate. Ammonia and TKN were significantly higher during the flooding suggesting that water coming in to the pond already contains high levels of said nutrients possibly due to higher organic load. Conversely, nitrite and nitrate levels were significantly higher during the draining suggesting transformation of ammonia into these less toxic substances by nitrifying bacteria
Heavy Metal Contamination in Water and Fishery Resources in Manila Bay Aquaculture Farms
Heavy metals (HM) are high-atomic weight elements hazardous at very low concentrations. Despite the health risk HM contamination brings, studies conducted were only confined to the offshore and marine portions of the bay. Hence, this study was conducted to establish baseline information and compare the spatial and seasonal distribution of heavy metal contamination in water and fishery resources in aquaculture farms and coastal areas in Manila Bay. Water and major aquaculture commodities were collected in November 2014, February 2015 and April 2015 and were analyzed for lead (Pb), cadmium (Cd), and mercury (Hg) using the following methods: (1) Graphite Furnace Atomizer-Atomic Absorption Spectrophotometry (GFA-AAS) for Pb and Cd and (2) Mercury Vaporizing Unit-AAS (MVU-AAS) for Hg. Cd (Bataan, Cavite, Bulacan, and Pampanga) and Hg (Cavite and Pampanga) in water were found significantly higher during the dry season (p < 0.05). In contrast, Pb in water was relatively higher during the wet season but levels were not significantly different with those in the dry. Several sites in Bataan, Bulacan, and Cavite, exceeded DENR regulatory limits for Pb and Hg in water by 1.35 to 1.8%. As for the fishery commodities, 2/12 milkfish samples and 1/9 exceeded regulatory limit for Pb in finfish (0.3 mg/kg) by 1.03 to 3.57% while 1/12 milkfish samples and 1/13 oyster samples exceeded the limit for Hg in bivalves (0.5 mg/kg) by 0.45 to 0.75%
Topiramate: Safety and Efficacy of Its Use in the Prevention and Treatment of Migraine
Migraine headaches are typically episodic in nature and may affect nearly 10% of the population. In addition to treatment, prevention of subsequent episodes or progression to a chronic migraine state is an important therapeutic area. Topiramate is a centrally acting medication approved for both the prevention of seizures and migraine headache. At this time, the exact mechanism of how topiramate assists in migraine prevention is unknown. Several large randomized, controlled trials have aided in establishing topiramate\u27s role in migraine prevention. Despite a favorable pharmacokinetic and adverse effect profile established in clinical trials, several additional studies, case reports and toxicology reports have demonstrated topiramate as a cause of cognitive and behavioural changes. The use of topiramate in migraine prevention can improve a patient\u27s quality of life and is a cost-effective option for migraine prevention
Assessing Within-Field Variation in Alfalfa Leaf Area Index Using UAV Visible Vegetation Indices
This study examines the use of leaf area index (LAI) to inform variable-rate irrigation (VRI) for irrigated alfalfa (Medicago sativa). LAI is useful for predicting zone-specific evapotranspiration (ETc). One approach toward estimating LAI is to utilize the relationship between LAI and visible vegetation indices (VVIs) using unmanned aerial vehicle (UAV) imagery. This research has three objectives: (1) to measure and describe the within-field variation in LAI and canopy height for an irrigated alfalfa field, (2) to evaluate the relationships between the alfalfa LAI and various VVIs with and without field average canopy height, and (3) to use UAV images and field average canopy height to describe the within-field variation in LAI and the potential application to VRI. The study was conducted in 2021–2022 in Rexburg, Idaho. Over the course of the study, the measured LAI varied from 0.23 m2 m−2 to 11.28 m2 m−2 and canopy height varied from 6 cm to 65 cm. There was strong spatial clustering in the measured LAI but the spatial patterns were dynamic between dates. Among eleven VVIs evaluated, the four that combined green and red wavelengths but excluded blue wavelengths showed the most promise. For all VVIs, adding average canopy height to multiple linear regression improved LAI prediction. The regression model using the modified green–red vegetation index (MGRVI) and canopy height (R2 = 0.93) was applied to describe the spatial variation in the LAI among VRI zones. There were significant (p \u3c 0.05) but not practical differences
Intrasexual competition and eating restriction in heterosexual and homosexual individuals
Restrictive eating attitudes and behaviors have been hypothesized to be related to processes of intrasexual competition. According to this perspective, within-sex competition for status serves the adaptive purpose of attracting mates. As such, status competition salience may lead to concerns of mating desirability. For heterosexual women and gay men, such concerns revolve around appearing youthful and thus, thinner. Following this logic, we examined how exposure to high-status and competitive (but not thin or highly attractive) same-sex individuals would influence body image and eating attitudes in heterosexual and in gay/lesbian individuals. Results indicated that for heterosexuals, intrasexual competition cues led to greater body image dissatisfaction and more restrictive eating attitudes for women, but not for men. In contrast, for homosexual individuals, intrasexual competition cues led to worse body image and eating attitudes for gay men, but not for lesbian women. These findings support the idea that the ultimate explanation for eating disorders is related to intrasexual competition
Development and validation of a multivariable prediction model for missed HIV health care provider visits in a large US clinical cohort
Background: Identifying individuals at high risk of missing HIV care provider visits could support proactive intervention. Previous prediction models for missed visits have not incorporated data beyond the individual level.
Methods: We developed prediction models for missed visits among people with HIV (PWH) with ≥1 follow-up visit in the Center for AIDS Research Network of Integrated Clinical Systems from 2010 to 2016. Individual-level (medical record data and patient-reported outcomes), community-level (American Community Survey), HIV care site-level (standardized clinic leadership survey), and structural-level (HIV criminalization laws, Medicaid expansion, and state AIDS Drug Assistance Program budget) predictors were included. Models were developed using random forests with 10-fold cross-validation; candidate models with the highest area under the curve (AUC) were identified.
Results: Data from 382 432 visits among 20 807 PWH followed for a median of 3.8 years were included; the median age was 44 years, 81% were male, 37% were Black, 15% reported injection drug use, and 57% reported male-to-male sexual contact. The highest AUC was 0.76, and the strongest predictors were at the individual level (prior visit adherence, age, CD4+ count) and community level (proportion living in poverty, unemployed, and of Black race). A simplified model, including readily accessible variables available in a web-based calculator, had a slightly lower AUC of .700.
Conclusions: Prediction models validated using multilevel data had a similar AUC to previous models developed using only individual-level data. The strongest predictors were individual-level variables, particularly prior visit adherence, though community-level variables were also predictive. Absent additional data, PWH with previous missed visits should be prioritized by interventions to improve visit adherence
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