Neural Tube Defects (NTDs) are a group of common congenital malformations that result from incomplete neural tube closure leading to abnormalities of the brain and/or spinal cord. Unfortunately, their etiology remains unknown, probably due to complex multifactorial interactions. The protective effect of dietary folates in preventing NTDs is well known, but this beneficial effect is limited to the 60 to 70% of cases; leaving 30% of the population without any known option for improving pregnancy outcomes. The mechanism by which folates rescue NTD-affected embryos is poorly understood, but the ability of folate supplementation to overcome a significant percentage of NTDs and the critical role of 5-methyltetrahydrofolate in the remethylation of homocysteine (Hcy) to methionine in the placenta suggests that folate binding and/or transport might play a critical role during development. We hypothesized that maternal autoantibodies (AB) targeting placental folate receptor alpha (FRα) are blocking the receptor and limiting the ability of the FRα to bind folates, reducing intraembryonic folate levels. Furthermore, we hypothesized that AB binding to other relevant proteins required for trophoblastic growth and placentation can be involved in activating pathologic inflammatory pathways that can result in suboptimal uptake of nutrients and contribute to an abnormal closure of the neural tube. We developed a high throughput ELISA to evaluate whether mothers experiencing pregnancies complicated with NTDs are more likely to have placental AB to FRα than are mothers experiencing normal pregnancies. We optimized and simplified a protocol for AB elution from placental tissues and determined whether these antibodies were blocking the FRα from binding with available folates. Although anti-FRα IgG antibodies were not associated to the blocking activity in this study, we found that the blocking activity was higher in the placentas from NTD-affected pregnancies compared to controls, that FRα IgM antibodies are most likely the type of antibody produced during gestation that is most relevant to the blocking activity and that it is unlikely that autoimmunity against other developmental proteins associated with NTDs is generating the NTDs. / text

The current study is the first to demonstrate that structural deficits in the Anterior Cingulate Cortex (ACC) of the human brain may play a role in reading ability. Recent imaging work has indicated that the ACC is activated by tasks involving modulation of the fronto-temporal networks during language processing tasks and may be involved in anticipatory reactions and response preparation during reading. This study investigated the relationship between ACC volumetric measurements and reading ability in a sample of 68 individuals nested within 24 families with and without reading disorders. This sample allowed for examination of the effect of the volume of the ACC on reading, while controlling for normally occurring fluctuations in the size of the ACC due to heredity and shared environment. Forty-five linear models were conducted in SPSS on all 68 participants using the brain measurements (ACC, ACC with Paracingulate (PaC), and Putamen, separately) as well as control variables (gender, FSIQ, family membership) as predictors of the outcomes variables related to reading achievement (GORT Passage, rate, and accuracy) and reading processes (CTOPP phonological awareness and rapid naming). The use of family membership as a random effect predictor together with the specific brain volume as a predictor allowed for the effect of family on reading outcomes to be accounted for while, explicitly accounting for any relationships that may exist between family and brain volume. Additional sets of measurements, with PaC, were included in the final analyses to address the inconsistent inclusion of this tertiary structure in earlier research. Finally, a control region (putamen) was included to rule out whole brain effects and improve the specificity of the findings. The most significant findings were that the results varied systematically with inclusion or exclusion of the PaC. Measurements including the PaC were statistically significant for reading achievement for the left side of the ACC as expected. However, for the ACC volume without PaC, it was the right side that was related to reading measures. Neither set of measurements of the ACC were predictive of group membership. The current study supported a role for the ACC in reading and suggests a standardized method for inclusion of the PaC in the volumetric analysis of the ACC. / text

Zinc Oxide (ZnO)is a wide band gap semiconductor which has attracted great attention because of its wide applicability. In order to obtain semiconductor devices with stable and reproducible properties further study of deep level defects is essential. DLTS (Deep level Transient Spectroscopy) is a direct and straightforward techniqueto determine the energy level of the deep level defects. Other information such as activation energy and capture cross section of the defect can also be obtained through this method. In our study ZnO single crystal samples were implanted by oxygen with the energy of 150keV. After the pretreatment of hydrogen peroxide, Schottky contacts were fabricated with Au film deposited by thermal evaporation. Deep level defects were studied by deep level transient spectroscopy (DLTS). Single peak spectra were observed in the as-implanted sample and samples anneal at 350oC, 650oC and 750oC with the corresponding activation energy decreasing with the annealing temperature from ~0.29eV as found in theas-implanted sample. Three peaks were identified in the DLTS spectra of the 900oC sample, with the activation energies of 0.11eV, 0.16eV and 0.37eV respectively.After analysis in detail we found some peaks in the DLTS spectra were the combination of two other peaks, dominated in different temperature range. The thermal evolutions of the deep levels up to the temperature of 1200oC were also investigated. / published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy

The effects of different process parameters on tribology and surface defects were studied till date, but there has been a very minimal study to understand the effect of slurry temperature during Copper Chemical Mechanical Polishing (CMP). The surface defects such as dishing, erosion and metal loss amount for more than 50% of the defects that hamper the device yield and mainly the electrical properties during the manufacturing process. In this research, the effect of slurry temperature on tribology, surface defects and electrical properties during copper CMP employing different pad materials and slurries has been explored. Experiments were conducted at different slurry temperatures maintaining all the other process parameters constant. Post polished copper samples were analyzed for their dishing and metal loss characteristics. From the results, it was seen that the coefficient of friction and removal rate increased with increase in slurry temperature during polishing with both types of polishing pads. This increase in removal rate is attributed to a combined effect of change in pad mechanical properties and chemical reaction kinetics. The experimental data indicated that the increase in slurry temperature results in an increase in amounts of metal dishing and copper metal loss for one type of slurry and defects decrease with increase in slurry temperature for other type of slurry. This phenomenon indicates the effect of temperature on chemical reaction kinetics and its influence on defect generation. This can be attributed due to the change in pad asperities due to change in pad mechanical properties and chemical kinetics with change in slurry temperature. The slurry temperature has an effect not only on the surface defects and tribology but also on the change in pad mechanical properties. The copper thin films peeled off at higher polishing temperatures, leading to adhesion failure. With increase in temperature the copper crystallinity, hardness and modulus increased. Further with increase in the defects the electrical properties of the devices also degraded drastically and even failed to operate at higher levels of dishing and metal loss. This research is aimed at understanding the physics governing the defect generation during CMP.

Not available / text

A numerical method is developed to determine the dynamic behavior of delamination and transverse cracks in multilayered plates. The plate is subjected to a time dependent antiplane shear stress field which is acting on the plate surfaces. The interaction of waves diffracted at the crack tip with those reflected at the plate boundaries and transmitted at the material interface makes the problem very complicated, so analytical study of this problem cannot be carried out with our present state of knowledge; hence the problem is solved numerically. The finite element equations are obtained by variational calculus applied in the frequency domain. Thus time intregration schemes are avoided, but time dependent response can still be obtained after inverting the frequency dependent response spectra numerically by Fast Fourier Transform (FFT) routine. Another advantage of the frequency domain analysis is that the resonance frequency can be easily detected from the sharp peaks of the response spectra. The numerical difficulty associated with the singular behavior of the stress field near the crack tip has been avoided by using quarter point elements. The numerical results obtained from this investigation are compared with analytical results to verify the accuracy of the method.

published_or_final_version / abstract / toc / Dentistry / Master / Master of Philosophy

published_or_final_version / abstract / toc / Electrical and Electronic Engineering / Master / Master of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy