An isoperibol calorimeter for the investigation of biochemical kinetics and isothermal titration calorimetry

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaf 52).Isothermal titration calorimetry is a technique used to measure the enthalpy change associated with a molecular binding interaction. From these data, the binding constant for the reaction can be determined. In the scope of a larger project to design a high sensitivity instrument for collecting such data, the current methods in isothermal titration calorimetry were investigated. Further calorimetric experience was acquired by designing a large scale calorimetric device. Dilution reactions with dimethyl sulfoxide and water were conducted to measure the excess enthalpy of binding. The inaccuracy of these measurements necessitated the more careful design of an isoperibol calorimeter. This calorimeter was modeled was an arrangement of coupled thermal masses and capacitances in order to fully understand its transient response to a thermal input. Dilution reactions and a neutralization reaction with HCl and NH40H were performed on the system and the results were used to make recommendations for the design of the future high sensitivity device.by Ovid Charles Amadi.S.B

A multi-dimensional microfluidic platform recapitulating chemotactic and morphogenic chemical gradients

Thesis (Ph. D. in Medical Engineering)--Harvard-MIT Program in Health Sciences and Technology, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 102-113).The requirement that individual cells be able to communicate with one another over a range of length scales is a fundamental prerequisite for the evolution of multicellular organisms. Often diffusible chemical molecules originate from a source and span the distance between cells in order to establish a line of communication - where the meaning of the signal is a function of both spatial and temporal chemical concentrations. In the case of chemotaxis, cells respond to concentration gradients to establish directionality. In the case of morphogenesis, cells respond to the magnitude of the local concentration field to regulate gene expression. Presented here is an in vitro platform, applicable in the contexts of chemotaxis and morphogenesis, where cells may be exposed to dynamic chemical concentration fields while cultured in a 3-dimensional macromolecular matrix. In the first generation system, cells are exposed to a one-dimensional gradient - constant along the two orthogonal axes. The second-generation system produces two orthogonally oriented gradients intersecting in a 2-dimensional field. These platforms were able to stimulate chemotaxis - both of cultured mammalian cells and emanating from murine skeletal muscle explants. Further, as a developmental tool, we were able to probe the role of Wnt signaling during Sonic Hedgehog based patterning of the vertebrate ventral neural tube. Using the presumptive enhancer for the p3 progenitor domain gene Nkx2.2, our findings indicate that such an enhancer would both negatively and positively regulate Nkx2.2 expression in response to Wnt signaling. However we found that the net effect of positive Wnt signaling - in the context of the cross-repressive interactions between various neural tube transcription factors (Nkx2.2, Olig2, and Pax6) - is inhibition of Nkx2.2 expression and p3 progenitor domain specification. On the basis of our new model, we postulate that the two opposing influences of Wnt on Sonic hedgehog signaling have distinct but dependent functions: first to inhibit Sonic Hedgehog signaling in the dorsal neural tube and secondly to prevent oscillatory behavior at the dorsal p3 boundary.by Ovid C. Amadi.Ph.D.in Medical Engineerin

Effects of transport on a biomass burning plume from Indochina during EMeRGe-Asia identified by WRF-Chem

The Indochina biomass burning (BB) season in springtime has a substantial environmental impact on the surrounding areas in Asia. In this study, we evaluated the environmental impact of a major long-range BB transport event on 19 March 2018 (a flight of the High Altitude and Long Range Research Aircraft (HALO; https://www.halo-spp.de, last access: 14 February 2023) research aircraft, flight F0319) preceded by a minor event on 17 March 2018 (flight F0317). Aircraft data obtained during the campaign in Asia of the Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales (EMeRGe) were available between 12 March and 7 April 2018. In F0319, results of 1 min mean carbon monoxide (CO), ozone (O$_3$), acetone (ACE), acetonitrile (ACN), organic aerosol (OA), and black carbon aerosol (BC) concentrations were up to 312.0, 79.0, 3.0, and 0.6 ppb and 6.4 and 2.5 µg m$^{−3}$, respectively, during the flight, which passed through the BB plume transport layer (BPTL) between the elevation of 2000–4000 m over the East China Sea (ECS). During F0319, the CO, O$_3$, ACE, ACN, OA, and BC maximum of the 1 min average concentrations were higher in the BPTL by 109.0, 8.0, 1.0, and 0.3 ppb and 3.0 and 1.3 µg m$^{−3}$ compared to flight F0317, respectively. Sulfate aerosol, rather than OA, showed the highest concentration at low altitudes (<1000 m) in both flights F0317 and F0319 resulting from the continental outflow in the ECS. The transport of BB aerosols from Indochina and its impacts on the downstream area were evaluated using a Weather Research Forecasting with Chemistry (WRF-Chem) model. The modeling results tended to overestimate the concentration of the species, with examples being CO (64 ppb), OA (0.3 µg m$^{−3}$), BC (0.2 µg m$^{−3}$), and O$_3$ (12.5 ppb) in the BPTL. Over the ECS, the simulated BB contribution demonstrated an increasing trend from the lowest values on 17 March 2018 to the highest values on 18 and 19 March 2018 for CO, fine particulate matter (PM$_{2.5}$), OA, BC, hydroxyl radicals (OH), nitrogen oxides (NO$_x$), total reactive nitrogen (NO$_y$), and O$_3$; by contrast, the variation of J(O$^1$D) decreased as the BB plume\u27s contribution increased over the ECS. In the lower boundary layer (<1000 m), the BB plume\u27s contribution to most species in the remote downstream areas was <20 %. However, at the BPTL, the contribution of the long-range transported BB plume was as high as 30 %–80 % for most of the species (NO$_y$, NO$_x$, PM$_{2.5}$, BC, OH, O$_3$, and CO) over southern China (SC), Taiwan, and the ECS. BB aerosols were identified as a potential source of cloud condensation nuclei, and the simulation results indicated that the transported BB plume had an effect on cloud water formation over SC and the ECS on 19 March 2018. The combination of BB aerosol enhancement with cloud water resulted in a reduction of incoming shortwave radiation at the surface in SC and the ECS by 5 %–7 % and 2 %–4 %, respectively, which potentially has significant regional climate implications

British Romanticism and the Global Climate

As a result of developments in the meteorological and geological sciences, the Romantic period saw the gradual emergence of attempts to understand the climate as a dynamic global system that could potentially be affected by human activity. This chapter examines textual responses to climate disruption cause by the Laki eruption of 1783 and the Tambora eruption of 1815. During the Laki haze, writers such as Horace Walpole, Gilbert White, and William Cowper found in Milton a powerful way of understanding the entanglements of culture and climate at a time of national and global crisis. Apocalyptic discourse continued to resonate during the Tambora crisis, as is evident in eyewitness accounts of the eruption, in the utopian predictions of John Barrow and Eleanor Anne Porden, and in the grim speculations of Byron’s ‘Darkness’. Romantic writing offers a powerful analogue for thinking about climate change in the Anthropocene

Metamorphoses

1st Editio