Microspore Wall Morphogenesis and Orbicule Ultrastructure of \u3ci\u3eIsoetes\u3c/i\u3e

The microspore wall morphogenesis and orbicule ultrastructure of Isoetes were studied using electron microscopy. Microspore wall morphogenesis in five species of Isoetes (I. appalachiana, I. engelmannii, I. hyemalis, I. piedmontana, and an undescribed species from York Co., VA, USA) was studied using scanning and transmission electron microscopy. Results show that they generally have the same developmental stages in terms of microspore wall morphogenesis. The mature microspore wall consisted of four layers: perispore, paraexospore, exospore and endospore. Paraexospore formation began during the tetrad stage. The exospore was then formed between the paraexospore and the plasma membrane. During the free spore stage, two walls were formed, the perispore and the endospore. The perispore develops on the surface of the paraexospore while the endospore was formed interior to the exospore and plasma membrane. Orbicule ultrastructure of nine species of Isoetes from the USA, Canada and Syria was studied, for the first time in the genus, using scanning electron microscopy. Orbicules are minute granules of sporopollenin observed on the inner wall of the secretory tapetum and their function remains unknown. Ultrastructural variation in orbicules of the nine studied species was documented. Orbicules were very variable in both shape and size

Emergency Landing and Guidance System

Every year there are thousands of aviation accidents along with hundreds of human deaths that happen around the world. While the data is sparse, it is well documented that many of these happen from emergency landings gone awry. While pilots can generally make great landings in clear daytime conditions, they are significantly handicapped when it comes to landing at night or amongst poor visibility conditions. Due to the nature of this problem and some of the large scale advances in software technology we propose a solution that provides a significant improvement from the status quo. Using transfer learning on neural networks to classify satellite images along with terrain elevation data from the USGS we are able to recreate maps that can readily direct pilots to locations that are relatively flat and lack structures or vegetation. Using San Luis Obispo as our data set we confirmed that we could correctly classify at least 93\% of landable terrain and then identified areas within that area that could safely be used to land a plane. We then transfer this data into a 3D rendering program that allows us to visualize what is happening. In additional to visualizing where the landing paths are we also create a landing algorithm that demonstrates how the plane will maintain its current glide path and navigate to a successful landing while avoiding obstacles

Writing apprehension and the computer classroom

This study was undertaken to determine if computers affect writing apprehension. Both experimental and clinical methodologies were employed in the form of surveys and interviews, respectively. The results indicate that computers have no measurable effect on students\u27 writing apprehension; Instructors\u27 backgrounds are examined, followed by their perceptions of writing apprehension and computers. The students\u27 experiences with computers and composition and their perceptions of writing apprehension and computers are also examined. Significant variations in experience and backgrounds brought to the classroom by both instructors and students indicate that writing apprehension is as individual as are students who experience it. These same results also indicate that instructors who must deal with writing apprehension cannot be expected to do so if they are unaware of its existence; This study concludes with a call for further research, particularly research which addresses the significance of the instructor to writing apprehensive students, computers or no

Should We Continue to Incarcerate Non-Violent Offenders?

This brief seeks to determine what types of offenses and offenders warrant punishment in prison and what types of offenders could be penalized using a community-based sanction. As one of the most expensive forms of punishment, prisons are designed to protect the community from people who pose a serious threat to the safety of the community, namely violent and predatory offenders. Studies show that many factors contribute to the crime rate, such as the state of the economy, the demand for illegal drugs, arrest patterns, and prevention efforts, among others. Higher incarceration rates play only a marginal role in overall crime reduction. In addition, stiffer penalties and longer prison sentences for non-violent and drug crimes will not necessarily increase public safety.Includes bibliographical reference

School-Based Juvenile Probation and Police Partnerships for Truancy Reduction

Truancy places students at risk in primary and secondary education and is linked to conduct disorder, drug use, and delinquency. To prevent truancy and reduce risk, school-based proba-tion supervision has emerged within school districts in partnership with local law enforcement officers in an effort to enforce probation conditions for truant youths and prevent future delin-quency. This research uses key information interviews of knowledgeable stakeholders to examine the delivery of school-based probation supervision. Home visits and court hearings were perceived to be effective at reducing truancy and tardiness. This study affirms that strong lead-ership, information sharing, and involvement of parents were 3 key factors related to truancy reduction

Gender and Serious Youth Victimization: Assessing the Generality of Self-Control, Differential Association, and Social Bonding Theories

Criminologists have long questioned whether theories that have focused on male delinquency are equally applicable to female delinquency, a phenomenon termed “gender generalizability.” While a number of studies have used self-reports from offenders, criminologists have yet to extend this issue to crime victims. While controlling for variables derived from victimization theories, we test three criminological perspectives (self-control, differential association, and social bond) on male and female victimization using data obtained from the Evaluation of the Gang Resistance Education and Training (GREAT) Program in the United States. Results show that for male victimization, gang membership and indications of a deviant lifestyle (self-reported delinquency) significantly predicted victimization, while associating with pro-social peers and being in a gang were associated with female victimization. Parental monitoring and belong to an intact family reduced victimization for males. Self-reported delinquency consistently predicted victimization across genders

Population-level antibiotic treatment policies in the setting of antibiotic resistance: A mathematical model of mass treatment of Helicobacter pylori in Mexico

Conference poster presented at the 39th Annual Meeting of the Society for Medical Decision Making Pittsburgh, Pennsylvania, October 22-25, 2017Purpose: Helicobacter pylori (H. pylori) is the strongest known risk factor for gastric cancer and peptic ulcer disease. Programs under consideration in high risk countries to prevent H. pylori- related diseases via broad population treatment could be complicated by increasing levels of antibiotic resistance (ABR). We evaluate the impact of different mass-treatment policies on H. pylori infection and ABR in Mexico using a mathematical model. Methods: We developed an age-structured, susceptible-infected-susceptible (SIS) transmission model of H. pylori infection in Mexico that included both treatment-sensitive and treatment- resistant strains. Antibiotic treatment was assumed to either clear sensitive strains or induce acquired resistance. In addition, the model included the effects of both background antibiotic use and antibiotic treatment specifically intended to treat H. pylori infection. Model parameters were derived from the published literature and estimated from primary data. Using the model, we projected H. pylori infection and resistance levels over 20 years without treatment and for three hypothetical population-wide treatment policies assumed to be implemented in 2018: (1) treat children only (2-6 year-olds); (2) treat older adults only (>40 years old); (3) treat everyone regardless of age. Clarithromycin -introduced in Mexico in 1991- was the antibiotic considered for the treatment policies. In sensitivity analyses, we considered different mixing patterns and trends of background antibiotic use. We validated the model against historical values of prevalence of infection and ABR of H. pylori. Results: In the absence of a mass-treatment policy, our model predicts infection begins to rise in 2021, mostly caused by treatment-induced resistant strains as a product of background use of antibiotics. The impact of the policies is immediate on decreasing infection but also increasing ABR (see Figure). For example, policy 3 decreases infection by 11% but increases ABR by 23% after the first year of implementation. The relative size of the decrease in infection is 50% the increase in ABR for policies 2 and 3, and 20% for policy 1. These results agree across all scenarios considered in sensitivity analysis. Conclusions: Conclusions: Mass-treatment policies have a higher effect on increasing ABR letting resistant strains take over infection. Given the high proportion of ABR at the time of the policy implementation, mass treatment strategies are not recommended for Mexico

Statistical and mathematical modeling to evaluate the cost-effectiveness of Helicobacter pylori screening and treating strategies in Mexico in the setting of antibiotic resistance

University of Minnesota Ph.D. dissertation. August 2017. Major: Health Services Research, Policy and Administration. Advisors: Karen Kuntz, Eva Enns. 1 computer file (PDF); ix, 128 pages.Helicobacter pylori (H. pylori), a bacterium that is present in the stomach of half of the world’s population with disproportionate burden in developing countries, is the strongest known biological risk factor for gastric cancer. Gastric cancer is the fourth most common type of cancer and the second cause of cancer death in the world. In particular, in Mexico gastric cancer is the third highest cause of cancer death in adults, with some regions having cancer mortality rates that are twice the national average (8.0 vs. 3.9 per 100,000, respectively). H. pylori can be treated with antibiotics, but widespread treatment may lead to significant levels of antibiotic resistance (ABR). ABR is one of the main causes of H. pylori treatment failure and represents one of the greatest emerging global health threats. In this thesis, we use statistical and mathematical modeling to investigate the health benefits, harms, costs and cost-effectiveness of screen-and-treat strategies for identifying and treating persons with H. pylori to inform public health practice in three steps. First, we estimated the age-specific force of infection of H. pylori --defined as the instantaneous per capita rate at which susceptibles acquire infection-- using a novel hierarchical nonlinear Bayesian catalytic epidemic model with data from a national H. pylori seroepidemiology survey in Mexico. Second, we developed an age-structured, susceptible-infected-susceptible (SIS) transmission model of H. pylori infection in Mexico that included both treatment-sensitive and treatment-resistant strains. Model parameters were derived from the published literature and estimated from primary data. Using the model, we projected H. pylori infection and resistance levels over 20 years without treatment and for three hypothetical population-wide treatment policies assumed to be implemented in 2018. In sensitivity analyses, we considered different mixing patterns and trends of background antibiotic use. We validated the model against historical values of prevalence of infection and ABR of H. pylori. Third, we expanded the SIS model to incorporate the natural history of gastric carcinogenesis including gastritis, intestinal metaplasia, dysplasia and ultimately non-cardia gastric cancer. We then estimated the cost-effectiveness of various screen-and-treat strategies for H. pylori infection and ABR in the Mexican population from the health sector perspective

Potential bias associated with modeling the effectiveness of treatment using an overall hazard ratio

Poster presented at the 36th Annual Meeting of the Society for Medical Decision Making in Miami, FL, October 2014Purpose: Clinical trials often report treatment efficacy in terms of the reduction of all-cause mortality [i.e., overall hazard ratio (OHR)], and not the reduction in disease-specific mortality [i.e., disease-specific hazard ratio (DSHR)]. Using an OHR to reduce all-cause mortality beyond the time horizon of the clinical trial may introduce bias if the relative proportion of other-cause mortality increases with age. We aim to quantify this bias. Methods: We simulated a hypothetical cohort of patients with a generic disease that increases the age-, sex-, and race-specific mortality rate (μASR) by a constant additive disease-specific rate (μDis). We assumed a DSHR of 0.75 (unreported) and an OHR of 0.80 (reported, derived from DSHR and assumptions of clinical trial population). We quantified the bias in terms of the difference in life expectancy (LE) gains with treatment between using an OHR approach to reduce all-cause mortality over a lifetime [(μASR+ μDis)xOHR] compared with using a DSHR approach to reduce disease-specific mortality [μASR+(μDis)xDSHR]. We varied the starting age of the cohort from 40 to 70 years old. Results: The OHR bias increases as DSHR decreases and with younger starting ages of the cohort. For a cohort of 60 year-old sick patients, the mortality rate under OHR approach crosses μASR at the age of 90 (see figure) and LE gain is overestimated by 0.6 years (a 3.7% increase). We also used OHR as an estimate of DSHR [μASR+(μDis)xOHR] (as the latter is not often reported). This resulted in a slight shift in the mortality rate compared to the DSHR approach (see figure), yielding in an underestimation of the LE gain. Conclusions: The use of an OHR approach to model treatment effectiveness beyond the time horizon of the trial overestimates the effectiveness of the treatment. Under an OHR approach it is possible that sick individuals at some point will face a lower mortality rate compared with healthy individuals. We recommend either to derive a DSHR from trials and use the DSHR approach, or to use the OHR as an estimate of DSHR in the model, which is a conservative assumption