Hochschild cohomology of socle deformations of a class of Koszul self-injective algebras

We consider the socle deformations arising from formal deformations of a class of Koszul self-injective special biserial algebras which occur in the study of the Drinfeld double of the generalized Taft algebras. We show, for these deformations, that the Hochschild cohomology ring modulo nilpotence is a finitely generated commutative algebra of Krull dimension 2.Comment: 10 pages. Minor changes, references updated. To appear in Colloq. Math

Radio Microlensing: Past, Present & Near Future

Strongly correlated non-intrinsic variability between 5 and 8.5 GHz has been observed in one of the lensed images of the gravitational lens B1600+434. These non-intrinsic (i.e. `external') variations are interpreted as `radio-microlensing' of relativistic micro-arsec-scale jet components in the source at a redshift of z=1.59 by massive compact objects in the halo of the edge-on disk lens galaxy at z=0.41. We shortly summarize these observations and discuss several new observational and theoretical programs to investigate this new phenomenon in more detail

Artificial Intelligence

Contains research objectives and reports on eight research projects.Computation Center, M.I.T

TESTING CAUSAL HYPOTHESES AND ASSOCIATIONS BETWEEN PERINATAL RISK FACTORS AND OFFSPRING MORBIDITY AND MORTALITY

The Developmental Origins of Health and Disease (DOHaD) hypothesis is a broad theoretical framework that highlights how early risk factors have a causal influence on later physical and psychopathological outcomes. Numerous studies have documented such associations and underlying mechanisms have been hypothesized. Most existing studies, however, have not been able to rule out the possibility of environmental and genetic confounding. Thus, concerns exist about causal interpretations of the statistical associations identified between early risk factors and later outcomes. The six projects in my dissertation use quasi-experimental designs to rigorously test causal inferences across perinatal risk factors and offspring outcomes. The first two projects use a natural experiment approach to compare risk and hypothesized mechanisms across sensitive periods of development. In particular, the random occurrence of maternal bereavement stress across the preconception, prenatal, and postnatal periods was studied as a risk factor for offspring infant mortality and child and adult psychiatric problems. The next pair of projects examined birth weight and physical, psychiatric, educational, and socioeconomic problems using a sibling-comparison design. The final two projects used cousin-comparisons to explore the parental correlates and offspring psychiatric and education problems associated with interpregnancy interval, or the duration between the birth of an earlier born sibling and the conception of following sibling. Across these projects, findings both support and refute previous causal claims and important novel associations are identified. These studies allowed for a thorough examination of the nature of the associations between several perinatal risk factors and offspring physical, psychiatric, educational, and socioeconomic problems. The projects illustrate how combining several quasi-experimental designs can specifically test the DOHaD hypothesis by ruling out plausible alternative hypotheses. My findings also inform the direction future DOHaD-based studies should pursue

A genetically informed study of the associations between maternal age at childbearing and adverse perinatal outcomes

We examined associations of maternal age at childbearing (MAC) with gestational age and fetal growth (i.e., birth weight adjusting for gestational age), using two genetically informed designs (cousin and sibling comparisons) and data from two cohorts, a population-based Swedish sample and a nationally representative United States sample. We also conducted sensitivity analyses to test limitations of the designs. The findings were consistent across samples and suggested that, associations observed in the population between younger MAC and shorter gestational age were confounded by shared familial factors; however, associations of advanced MAC with shorter gestational age remained robust after accounting for shared familial factors. In contrast to the gestational age findings, neither early nor advanced MAC was associated with lower fetal growth after accounting for shared familial factors. Given certain assumptions, these findings provide support for a causal association between advanced MAC and shorter gestational age. The results also suggest that there are not causal associations between early MAC and shorter gestational age, between early MAC and lower fetal growth, and between advanced MAC and lower fetal growth.NonePublishe

Automatic Mechanism Generation for Pyrolysis of Di-Tert-Butyl Sulfide

The automated Reaction Mechanism Generator (RMG), using rate parameters derived from ab initio CCSD(T) calculations, is used to build reaction networks for the thermal decomposition of di-tert-butyl sulfide. Simulation results were compared with data from pyrolysis experiments with and without the addition of a cyclohexene inhibitor. Purely free-radical chemistry did not properly explain the reactivity of di-tert-butyl sulfide, as the previous experimental work showed that the sulfide decomposed via first-order kinetics in the presence and absence of the radical inhibitor. The concerted unimolecular decomposition of di-tert-butyl sulfide to form isobutene and tert-butyl thiol was found to be a key reaction in both cases, as it explained the first-order sulfide decomposition. The computer-generated kinetic model predictions quantitatively match most of the experimental data, but the model is apparently missing pathways for radical-induced decomposition of thiols to form elemental sulfur. Cyclohexene has a significant effect on the composition of the radical pool, and this led to dramatic changes in the resulting product distribution

Optimized Robust Adaptive Networks in Supervisory Control and Data Acquisition Systems

This thesis investigates the application of a Exponential Weighted Moving Average (EWMA) to be used as a memory buffer in conjunction with Special Protection Schemes (SPS) using the Electric Power and Communication Synchronizing Simulator (EPOCHS). It is proposed that using an SPS incorporating EWMA can compensate for the network layer lack of guarantee of packet delivery and provide for the stability and integrity of the power grid under a catastrophic event. The performance of the proposed SPS is evaluated using a discrete event computer simulation developed using the NS2 network simulator and the Power System Simulator for Engineering (PSS/E) power system simulator. Performance and metrics evaluated in terms of the SPS’s ability to properly calculate disturbance size and to react to the disturbance before the system reaches the minimum frequency threshold of 58.8 HZ and before 0.5 second threshold. Experimental results indicate that the proposed SPS with EWMA can be successfully be applied to ensure power grid stability regardless of network background traffic. The results indicate that the proposed EWMA SPS ensures the protection of the grid. The EWMA SPS has a significant impact on performance when applied to a heavy background traffic network without router reservation enabling it to be stable without the additional hardware cost. Overall, in the tested configuration, the new SPS system successfully maintained steady state operation under all traffic intensities