S.J. Mason. / "August 25, 1953." / Army Signal Corps Contract DA 36-039 sc-100 Project 8-102B-0 Dept. of the Army Project 3-99-10-022

C.A. Stutt. / "March 26, 1949." / Bibliography: p. 18. / Army Signal Corps Contract No. W36-039-sc-32037 Project No. 102B Dept. of the Army Project No. 3-99-10-022

B. Chance, J.N. Thurston, P.L. Richman. / "Reprinted from the Review of scientific instruments, v. 18, no. 9, 610-616, Sept., 1947." / Includes bibliographical references.

Neural tube defects (NTDs) are malformations affecting about 2.6/1000 births worldwide, and 1/1000 in the United States. Their etiology remains unknown, and is likely due to interaction of genetic susceptibility factors with environmental exposure. Of the many environmental agents considered to potentially contribute to NTD risk, arsenic is one that is surrounded in controversy. We have developed a model system utilizing maternal intraperitoneal (I.P.) exposure on E7.5 and E8.5 to As 9.6 mg/kg (as sodium arsenate) in a normal inbred mouse strain, LM/Bc/Fnn, that is sensitive to arsenate-induced exencephaly. We investigated arsenate induced gene expression changes using DNA microarrays of embryonic anterior neural tube tissue, as well as monitoring of metabolic function in conjunction with the administration of select compounds to rescue the normal phenotype. Finally, to address questions concerning the importance of route of administration and potential maternal toxicity, a teratology study was performed using three arsenate doses administered orally. Regarding the gene expression study, we identified several candidate genes and ontology groups that may be responsible for arsenate’s teratogenicity. Genes include: engrailed 1 (En-1), platelet derived growth factor receptor alpha (Pdgfrα) and ephrinA7 (EphA7). Gene ontology groups identified include oxidative phosphorylation, redox response, and regulation of I-kappaB kinase/NF-kappaB cascade. Acute arsenate exposure induced disruption of mitochondrial function and dependent glucose homeostasis: subsequent hyperglycemia was teratogenic. Maternal treatment with insulin or n-acetyl cysteine, an antioxidant and precursor of glutathione synthesis, proved highly successful in rescuing both the normal phenotype, and to differing degree, the maternal hyperglycemia. Maternal oral arsenate administration also resulted in exencephaly, with exposed embryos exhibiting a positive linear trend with arsenate dosage. There were also linear trends in the relationships between arsenate dose and anomalies involving several components of the axial skeleton: the vertebrae and calvarium. There was no evidence of maternal toxicity as shown by lack of differences in maternal body weight gain, liver, and kidney weights. In conclusion, maternal arsenate exposure (regardless of exposure route) was teratogenic in our model, primarily causing NTDs. Responsible mechanisms may involve disruption of redox and glucose homeostasis as well as expression of established NTD candidate genes.

Obesity in pregnancy has been associated with an elevated risk for neural tube defects, though it is unknown if this is linked to a lower folate status in obese women. Studies have identified a reduced folate status among obese women even after controlling for folate intake. Thus, it is possible that folic acid pharmacokinetics are altered in the obese body. In this study, we compared the pharmacokinetics of folic acid in obese and non-obese women of childbearing age, following administration of a weight-adjusted dose. Area under the concentration-time curve was found to be significantly higher in the obese group, with the dose per kilogram lean body weight most strongly predicting systemic exposure. Estimation of the daily dose required to achieve protective blood concentrations did not identify a need to change supplementation recommendations for obese women. Accordingly, current guidelines appear to suggest adequate doses for obese women of childbearing age.

Obesity in pregnancy has been associated with an elevated risk for neural tube defects, though it is unknown if this is linked to a lower folate status in obese women. Studies have identified a reduced folate status among obese women even after controlling for folate intake. Thus, it is possible that folic acid pharmacokinetics are altered in the obese body. In this study, we compared the pharmacokinetics of folic acid in obese and non-obese women of childbearing age, following administration of a weight-adjusted dose. Area under the concentration-time curve was found to be significantly higher in the obese group, with the dose per kilogram lean body weight most strongly predicting systemic exposure. Estimation of the daily dose required to achieve protective blood concentrations did not identify a need to change supplementation recommendations for obese women. Accordingly, current guidelines appear to suggest adequate doses for obese women of childbearing age.

In this thesis, motivated by modelling polymers, the topological entanglement complexity of systems of two self-avoiding polygons (2SAPs), stretched polygons and systems of self-avoiding walks (SSAWs) in a tubular sublattice of Z3 are investigated. In particular, knotting and linking probabilities are used to measure a polygonfs selfentanglement and its entanglement with other polygons respectively. For the case of 2SAPs, it is established that the homological linking probability goes to one at least as fast as 1-O(n^(-1/2)) and that the topological linking probability goes to one exponentially rapidly as n, the size of the 2SAP, goes to infinity. For the case of stretched polygons, used to model ring polymers under the influence of an external force f, it is shown that, no matter the strength or direction of the external force, the knotting probability goes to one exponentially as n, the size of the polygon, goes to infinity. Associating a two-component link to each stretched polygon, it is also proved that the topological linking probability goes to unity exponentially fast as n→∞. Furthermore, a set of entangled chains confined to a tube is modelled by a system of self- and mutually avoiding walks (SSAW). It is shown that there exists a positive number γ such that the probability that an SSAW of size n has entanglement complexity (EC), as defined in this thesis, greater than γn approaches one exponentially as n→∞. It is also established that EC of an SSAW is bounded above by a linear function of its size. Using a transfer-matrix approach, the asymptotic form of the free energy for the SSAW model is also obtained and the average edge-density for span m SSAWs is proved to approach a constant as m→∞. Hence, it is shown that EC is a ggoodh measure of entanglement complexity for dense polymer systems modelled by SSAWs, in particular, because EC increases linearly with system size, as the size of the system goes to infinity.

In the current situation is the straight tube cutter, that provides Luvata’s line of large recoolers with copper tubes, manually operated. To prevent damages and facilitate mounting the tubes must be properly arranged when they leave the machine. This report aims to investigate and present an automated solution where the operator does not need to participate in the process. A number of theories have been drawn up and tests have been done. The results show that the in principle best solution is to have a leaning carrier that’s automatically height-adjusted by two lift tables underneath. The height adjustment keeps a constant distance between the top tube layer and rollover protection bars on the machine. That is done to allow the carrier to have a high enough angle to ensure that the tubes roll down even if they aren’t completely straight, but without rolling over the previous tubes. To evaluate the solutions Ulrich and Eppingers method for Concept scoring was used. This method means that the various solutions are scored and weighted based on a number of criteria’s, and the output is measurable results.

In this thesis, motivated by modelling polymers, the topological entanglement complexity of systems of two self-avoiding polygons (2SAPs), stretched polygons and systems of self-avoiding walks (SSAWs) in a tubular sublattice of Z3 are investigated. In particular, knotting and linking probabilities are used to measure a polygonfs selfentanglement and its entanglement with other polygons respectively. For the case of 2SAPs, it is established that the homological linking probability goes to one at least as fast as 1-O(n^(-1/2)) and that the topological linking probability goes to one exponentially rapidly as n, the size of the 2SAP, goes to infinity. For the case of stretched polygons, used to model ring polymers under the influence of an external force f, it is shown that, no matter the strength or direction of the external force, the knotting probability goes to one exponentially as n, the size of the polygon, goes to infinity. Associating a two-component link to each stretched polygon, it is also proved that the topological linking probability goes to unity exponentially fast as n→∞. Furthermore, a set of entangled chains confined to a tube is modelled by a system of self- and mutually avoiding walks (SSAW). It is shown that there exists a positive number γ such that the probability that an SSAW of size n has entanglement complexity (EC), as defined in this thesis, greater than γn approaches one exponentially as n→∞. It is also established that EC of an SSAW is bounded above by a linear function of its size. Using a transfer-matrix approach, the asymptotic form of the free energy for the SSAW model is also obtained and the average edge-density for span m SSAWs is proved to approach a constant as m→∞. Hence, it is shown that EC is a ggoodh measure of entanglement complexity for dense polymer systems modelled by SSAWs, in particular, because EC increases linearly with system size, as the size of the system goes to infinity.

The operation of pulse tube cryocoolers (PTCs) is based on complicated and poorly-understood solid-fluid interactions involving periodic flows of a cryogenic fluid in a flow loop that includes components filled with micro porous structures. CFD simulation is the current trend in modeling of pulse-tube cryocoolers. Such simulations can only be meaningful if correct closure relations are available. The objective of this investigation is to measure and empirically correlate the axial hydrodynamic parameters for two widely used cryocooler regenerator structures. A test section will be designed, constructed and instrumented for the measurements. Porous structures tested will include 325 and 400-Mesh stainless screens, each at two different porosities. Tests will be performed with helium as the working fluid, over a wide range of parameters. The longitudinal permeabilities and Forchheimer s inertial coefficients will then be obtained in an iterative process where agreement between the data and the predictions of detailed CFD simulations for the entire test sections and their vicinity are sought. Empirical correlations representing the longitudinal permeability and Forchheimer s coefficient in terms of relevant dimensionless parameters will then be developed.