Interactive substrate for bone regeneration

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.Includes bibliographical references (leaves 59-68).Current methods of bone repair rely on autografts (bone from a donor site) and allografts (bone from human cadaver). However, these methods are plagued with disadvantages. There is a clear and urgent need to provide alternatives for regenerating and repairing bone. Bone is known to be one of the many connective tissues in the body that are responsive to exogenous electrical stimulation. Based on this principle, this thesis explores the potential of using an electrically conducting polymer, polypyrrole, as a substrate for bone regeneration. Optically transparent thin films of polypyrrole, with a polyanionic dopant, poly(styrenesulfonate), were synthesized electrochemically and characterized by X-Ray Photoelectron Spectroscopy, UV/VIS spectroscopy, Scanning Electron Microscopy and by electrical conductivity measurements. In this study, Bone Marrow Stromal Cells (BMSC), which are the progenitor cells to bone cells (osteoblasts), were used as the in vitro model system. Their viability, proliferation and differentiation capabilities were evaluated on polypyrrole, in the absence and presence of electrical stimulation. Results indicate that polypyrrole is ideally suited as a substratum for BMSC growth and differentiation. The application of an electrical stimulus through the polypyrrole substrate was found to induce the differentiation of BMSC towards an osteogenic lineage. Thus, polypyrrole, by virtue of its conductive properties, its in vitro biocompatibility and its flexibility in altering surface characteristics, has an exciting potential as a suitable interactive substrate for bone regeneration.by Nahid Rahman.S.M

Financial Anxieties of Large, Medium and Small Enterprises in japan

In our previous article (2005), we investigated financial anxieties over the economy of Japan by treating the conditional variances of TARCH model as the financial anxieties. However we did not distinguish between large enterprises and small enterprises, though we differentiated the financial anxieties between all enterprises and small enterprises. The reason was that we implicitly assumed that the financial anxieties of large firms were smaller than those of small firms in the period of financial distrss, since lerge firms could access the credit markets directly through stock and bond market. Small firms which were more dependent of bank loans were supposed to have much more finanncial anxieties in the finanncial panic than large firms.In this article, we have quantified the financial anxieties for four different catedories of enterprises:large enterprises, medium enterprises, small enterprises and adding altogether (viz., large + medium + small) as all enterprises. Also another new aspest is that we have used EGARCH model instesd of TARCH, because in this model there is no need for non-negative constraints on the parameters and more importantly, it also allows for asymmetries in the variance equation. Then we have compared and explained financial anxieties for all categories through the line of history of the deflationary economy of Japan.Our findings show the opposite results that was expected. That is to say, large firms respond to financial distress more strongly than small firms

Systems of education governance and cultures of justice in Ireland, Scotland and Pakistan

This chapter compares the issue of cultures of justice in the systems of education governance in three education systems: Ireland, Scotland and Pakistan. The focus for the comparison are the current policies which shape the regulation of education. These policies were reviewed to identify key issues relating to social justice and equality, decision-making and accountability. From the analysis of each system, three central issues were identified: firstly, the improvement of a state education system; secondly, the degree of decentralisation and centralisation in governance structures and thirdly, the expectations placed on school leaders. The chapter concludes by discussing the tensions between the drive for system improvement and opportunities for school leaders to build strategies to address issues of inequality in schools

Single layer MoS2 on the Cu(111) surface: First-principles electronic structure calculations

First-principles calculations of the geometric and electronic structures of a single layer of molybdenum disulfide (MoS2) on Cu(111) utilizing the van der Waals density functional show three energetically equivalent stacking types and a Moire pattern whose periodicity is in agreement with experimental findings. The layer is found not to be purely physisorbed on the surface, rather there exists a chemical interaction between it and the Cu surface atoms. We also find that the MoS2 film is not appreciably buckled, while the top Cu layer gets reorganized and vertically disordered. The sizes of Moire patterns for a single layer of MoS2 adsorbed on other close-packed metal surfaces are also estimated by minimizing the lattice mismatch between the film and the substrate

Estimation of Precautionary Demand Caused by Financial Anxieties

Pioneering work of modelling financial anxieties was given by Kimura et al. (1999) as psychological change of people due to financial shocks. Since they regressed financial position (easy or tight) by nonstationary interest rate, their results exhibit high peaks not only in financial crisis period of 1997 and 1998, but also in the bubble economy period of 1987 to 1989, which seems to be a spurious regression. Furthermore, defining financial anxieties as the conditional variance in TARCH model, one of estimated coefficients does not satisfy sign condition. We got rid of these difficulties by introducing a growth rate model, where a change of financial position (toward ’tight’) under a change of interest rate (toward ’fall’) is regarded as financial anxieties. Such anxieties are quantified by conditional variance of EGARCH model and shown to be stationary. Precautionary demand caused by financial anxieties is estimated in VEC model and it is shown that money adjusted by precautionary demand satisfies a long-run equilibrium relationship in the system (adjusted money, real GDP, interest rate) even in the interval 1980q1 to 2003q2

Examination of the risk of reinfection with hepatitis C among injecting drug users who have been tested in Glasgow

Unsafe injecting practices put injecting drug users (IDUs) at repeat exposure to infection with the hepatitis C virus (HCV). It has not yet been determined if spontaneously clearing one's primary infection influences the risk of reinfection; our aim was to estimate the relative risk of reinfection in IDUs who have cleared the virus. We conducted a retrospective study using a large database of HCV test results covering Greater Glasgow Health Board during 1993–2007 to calculate rates of infection and reinfection in current/former IDUs. The relative risk of (re)infection in previously infected compared with never-infected IDUs was estimated using Poisson regression, adjusting for age at study entry, sex, and calendar period of test. Although the rate of reinfection in IDUs who were HCV antibody-positive, RNA-negative at baseline was lower (7/100 person-years, 95% CI: 5–9) than the rate of acute infection in IDUs who were HCV antibody-negative at baseline (10/100 person-years, 95% CI: 9–12), the risk of reinfection was not significantly different than the risk of initial infection (adjusted rate ratio = 0.78, 95% CI: 0.57–1.08). We found only weak evidence for a reduced risk of HCV reinfection in IDUs who had cleared their previous infection. Further research among those who have cleared infection through antiviral therapy is needed to help inform decisions regarding treatment of IDUs

Genomic and epigenomic changes in transgenerational response to cold stress in Arabidopsis thaliana

Plants are continuously exposed to various environmental stresses. They employ numerous strategies of resistance and develop a memory of stress exposure for future generations. Abiotic stress, like cold, can prompt the changes in phenotype, genotype, and epigenotype of plants. Plants can establish these as somatic and transgenerational memories. We studied the Arabidopsis thaliana plants exposed to multiple generations of cold stress. We hypothesized that the progeny of plants exposed to 25 generations to cold stress would be genetically and epigenetically more diverse than the parental plants. Our study reveals that multigenerational exposure to cold stress resulted in the physiological changes, as well as changes in the genomic and epigenomic (DNA methylation) patterns across generations. The main changes in the progeny were due to the high frequency of genetic mutations rather than epigenetic changes. Our work supports the existence of transgenerational stress response in plants and demonstrates that genetic changes prevail

Templates for positive and negative control Toffoli networks

Circuit realizations obtained from existing logic synthesis approaches may not be optimal and thus one commonly applies post-synthesis optimization techniques to get better realization of the circuits. This thesis proposes two new templates (templates 4 and 7) for positive and negative control Toffoli gates as well as proposing algorithms for post synthesis optimization of reversible positive and negative control Toffoli networks by utilizing the set of templates. When applying the templates to circuits generated by the improved shared cube synthesis approach [23] a reduction in quantum cost was achieved for 86 of the 110 circuits. On average a 21.34% reduction in quantum cost was achieved, and in some cases up to 53.58% reduction was obtained.Natural Sciences and Engineering Research Council of Canada (NSERC

Climate-influenced migration in Bangladesh: the need for a policy realignment

Recent research into migration in Bangladesh has highlighted that people migrate for better livelihoods, not necessarily in response to climatic stresses and shocks. If facilitated appropriately, internal and international migration can help build adaptive capacity to future environmental and climatic hazards. In this framing, migration happens in the context of a growing city-centred economy that promotes remittances to villages. However, a textual analysis of current and recent policies concerning climate change, development and poverty alleviation, and disaster management shows that the economic and adaptive roles of internal migration are often not included in policy framing. We argue that if migration works as a positive step towards adaptation, then the key challenge is to align the policies with this new understanding