A semi-empirical representation of the temporal variation of total greenhouse gas levels expressed as equivalent levels of carbon dioxide

Abstract and PDF report are also available on the MIT Joint Program on the Science and Policy of Global Change website (http://globalchange.mit.edu/).In order to examine the underlying longer-term trends in greenhouse gases, that are driven for example by anthropogenic emissions or climate change, it is useful to remove the recurring effects of natural cycles and oscillations on the sources and/or sinks of those gases that have strong biological (e.g., CO2, CH4, N2O) and/or photochemical (e.g. CH4) influences on their global atmospheric cycles. We use global observations to calculate monthly estimates of greenhouse gas levels expressed as CO2 equivalents, and then fit these estimates to a semi-empirical model that includes the natural seasonal, QBO, and ENSO variations, as well as a second order polynomial expressing longer-term variations. We find that this model provides a reasonably accurate fit to the observation-based monthly data. We also show that this semiempirical model has some predictive capability; that is it can be used to provide a reasonably reliable estimate of CO2 equivalents at the current time using validated observations that lag real time by a few to several months.This study received support from the MIT Joint Program on the Science and Policy of Global Change, which is funded by a consortium of government, industry and foundation sponsors

The Robotic Palomar 60-Inch Optical Afterglow Catalog: 2007

We present here the photometric results of the Robotic Palomar 60-inch Telescope (P60) observations for GRB optical afterglows. The quick response time and the size of the telescope allows us to observe the optical transients through V, R, I, g', i', z' filters, sometimes as early as 0.01 day after the trigger. Comparing the data obtained with the various filters we were able to compute color indices for the 1 day after the trigger epoch. The observations lasts until the OT fades below the detection threshold

Gas flow and fluidization in a thick dynamic regolith: A new mechanism for the formation of chondritic meteorites

We have previously shown that size and density sorting in a regolith which has been 'fluidized' by the passage or gases from the interior or the body can quantitatively explain metal-silicate fractionation, an important property of ordinary chondrites. Here we discuss whether the flow rates and flux or volatiles expected from a primitive parent body are likely to be sufficient for this mechanism. Many meteorite parent bodies may have contained volatiles. From a consideration of heat diffusion and fluid mechanics, we calculate the gas flow rate of volatiles (e.g., water) in the regolith of an asteroid-sized object heated by Al-26. Our calculations show that the flow velocities and flux of water vapor are sufficient to produce conditions suitable for fluidization. Other heat sources have yet to be considered, but literature work suggests that they may be equally effective

Experimental validation of shear-mediated contributions to multiple scattering in concentrated random dispersions of spherical particles

Experimental validation of shear-mediated contributions to multiple scattering in concentrated random dispersions of spherical particle

Modelling viscous boundary layer dissipation effects in liquid surrounding individual solid nano and micro-particles in an ultrasonic field

Upon application of ultrasonic waves to a suspension of solid particles in liquid, multiple scattering occurs at the particle/liquid interfaces leading to attenuation. It was recently shown through experimental verification that multiple scattering theory must include shear wave influences at the boundary between the liquid and solid particles in a nanofluid when the concentration of the scatterers is even as low as a few percent by volume. Herein, we consider silica spheres of 50−450 nm diameter in the long-wavelength regime to elucidate the form of the shear decay fields at the liquid/solid interface for individual particles. This is important because the overlap of these fields ultimately leads to the conversion of a compressional wave to shear waves and back into the compressional wave, the effect originating due to the density contrast between the particle and the liquid. Therefore, we examine in detail the velocity, vorticity and viscous dissipation in the shear wave field and around the silica spheres using finite element modelling, giving clarity to the viscous boundary effects. We also compare the numerical modelling to semi-analytical results

Chondrule formation, metamorphism, brecciation, an important new primary chondrule group, and the classification of chondrules

The recently proposed compositional classification scheme for meteoritic chondrules divides the chondrules into groups depending on the composition of their two major phases, olivine (or pyroxene) and the mesostasis, both of which are genetically important. The scheme is here applied to discussions of three topics: the petrographic classification of Roosevelt County 075 (the least-metamorphosed H chondrite known), brecciation (an extremely important and ubiquitous process probably experienced by greater than 40% of all unequilibrated ordinary chondrites), and the group A5 chondrules in the least metamorphosed ordinary chondrites which have many similarities to chondrules in the highly metamorphosed 'equilibrated' chondrites. Since composition provides insights into both primary formation properties of the chondruies and the effects of metamorphism on the entire assemblage it is possible to determine the petrographic type of RC075 as 3.1 with unique certainty. Similarly, the near scheme can be applied to individual chondrules without knowledge of the petrographic type of the host chondrite, which makes it especially suitable for studying breccias. Finally, the new scheme has revealed the existence of chondrules not identified by previous techniques and which appear to be extremely important. Like group A1 and A2 chondrules (but unlike group B1 chondrules) the primitive group A5 chondruies did not supercool during formation, but unlike group A1 and A2 chondrules (and like group B1 chondrules) they did not suffer volatile loss and reduction during formation. It is concluded that the compositional classification scheme provides important new insights into the formation and history of chondrules and chondrites which would be overlooked by previous schemes

Real Time Infrared Array IC

School of Electrical and Computer Engineerin

Engineering of industrial biocatalysts

In the last 40 years advances in the protein engineering have prompted the application of biocatalysts in the synthesis of building blocks, fine and bulk active pharmaceutical chemicals for the agrochemical, food, biofuel and pharmaceutical industries. Computational chemistry methodologies are fueling the development of a new generation of rationally designed biocatalysts with enhanced selectivity and specificity at a fraction of the time and cost compared to traditional protocols such as directed evolution. We present two examples of rational enzyme design. Our first example is the study of the phenylacetone monooxygenase (PAMO), the most stable and thermo-tolerant member of the Baeyer–Villiger monooxygenases family. We solved the catalytic mechanism of this enzyme for the native substrate phenylacetone as well as for a linear non-native substrate 2-octanone, using molecular dynamics simulations, quantum mechanics and quantum mechanics/molecular mechanics calculations.1 By studying relevant PAMO variants we provide a theoretical basis for the preference of the enzyme for the native aromatic substrate over non-native linear substrates.2 The second example regards an (S)-selective-transaminase from Vibrio fluvialis (S-TAm), which offers an environmentally sustainable synthesis route for the production of pure chiral amines.3 By applying a rational enzyme engineering protocol we altered this enzyme towards better acceptance of bulky ketones, starting with no detectable activity of the WT. Our best S-TAm variant improved the reaction rate by \u3e 1716-fold and retained activity even at 50 °C. To obtain such an outstanding result we only screened 113 variants, a substantially lower number than those typically associated with directed evolution (104 to 107 clones). Both studies provide fundamental insights into the rational engineering of enzymes for industrial applications. (1) Carvalho, A. T. P.; Dourado, D. F. A. R.; Skvortsov, T.; Abreu, M. de; Ferguson, L. J.; Quinn, D. J.; Moody, T. S.; Huang, M. Catalytic Mechanism of Phenylacetone Monooxygenases for Non-Native Linear Substrates. Phys. Chem. Chem. Phys. 2017, 19 (39), 26851–26861. https://doi.org/10.1039/C7CP03640J. (2) Carvalho, A. T. P.; Dourado, D. F. A. R.; Skvortsov, T.; Abreu, M. de; Ferguson, L. J.; Quinn, D. J.; Moody, T. S.; Huang, M. Spatial Requirement for PAMO for Transformation of Non-Native Linear Substrates. Phys. Chem. Chem. Phys. 2018, 20 (4), 2558–2570. https://doi.org/10.1039/C7CP07172H. (3) Dourado, D. F. A. R.; Pohle, S.; Carvalho, A. T. P.; Dheeman, D. S.; Caswell, J. M.; Skvortsov, T.; Miskelly, I.; Brown, R. T.; Quinn, D. J.; Allen, C. C. R.; Huang, M; Moody, T. Rational Design of a (S)-Selective-Transaminase for Asymmetric Synthesis of (1S)-1-(1,1′-Biphenyl-2-Yl)Ethanamine. ACS Catal. 2016, 6 (11), 7749–7759. https://doi.org/10.1021/acscatal.6b0238