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

Simulating broken PT\cal PT-symmetric Hamiltonian systems by weak measurement

By embedding a $\cal PT$-symmetric (pseudo-Hermitian) system into a large Hermitian one, we disclose the relations between $\cal{PT}$-symmetric Hamiltonians and weak measurement theory. We show that the amplification effect in weak measurement on a conventional quantum system can be used to effectively simulate a local broken $\cal PT$-symmetric Hamiltonian system, with the pre-selected state in the $\cal PT$-symmetric Hamiltonian system and its post-selected state resident in the dilated Hamiltonian system.Comment: 4 pages; with Supplemental Materia

Minimum Decomposition on Maxmin Trees

Maxmin trees are trees that consist of nodes that are either local minimums or maximums. Such trees were first studied by Postnikov. Later Dugan, Glennon, Gunnells, and Steingrimsson introduced the concept of weight to these trees and proved a bijection between maximum weight maxmin trees and permutations, defining weights for permutations. In addition, the q-Eulerian polynomial $E_n(x, q)$ is defined which relates descents and weights of permutations. This polynomial was later proven to exhibit a stabilization phenomenon by Agrawal et al. Extracting the formal power series $W_d(t)$ from the stabilization of these coefficients, $W_d(t)$ was conjectured to partially correspond to A256193. In our paper, we introduce a process called minimum decomposition to help us better understand maxmin trees. Using minimum decomposition, we present a new way to calculate the weight of different maxmin trees and prove the bijection between the coefficients of $W_d(t)$ and A256193.Comment: JMM. 8 page

Flexible parylene-based 3-D coiled cable

Prosthesis systems require reliable and flexible connecting cables from the sensing/stimulating electrode sites to processing circuitries. However, the limitations on the fabrication materials and processes restrict the cables' ability to stretch, resulting in breakage and failure of the implanted cabled device. Thus, a microfabricated and fully implantable 3-D parylene coiled cable for prosthesis application is presented. Compared to traditional flexible cables, this parylene coiled structure is able to be stretched by 100% of its original length and is also long-term biocompatible. In addition, the cable structure can be heat-formed in a mold to match muscle curvature and sharp turns in testing subjects and can also be directly integrated with flexible multi-electrodes arrays and neural probes

Sludge Digestion By Anaerobic Fluidized Beds. I: Lab Performance Data

This study was undertaken to evaluate the laboratory performance of the anaerobic fluidized bed digesting secondary biological sludge at 35° C with four hydraulic-retention times (HRTs): 1, 2.5, 5, and 10 days. In addition, the effects of both operating temperature (15° C, 25° C and 35° C) and the initial sludge solubilization on the digester performance were also examined. It was found that at 35° C, an adequate degree of sludge digestion was obtainable with an HRT of only 1-2 days if the influent biological sludge was presolubilized by treatment with 17.5 meq/L of sodium hydroxide. If no presolubilization was used, the necessary HRT was increased to 10 days. When the temperature was decreased to 25° C and the sludge was presolubilized, the required HRT was 2.5-3 days. However, as the temperature was further decreased to 15° C, the system was unable to achieve adequate digestion in as long as 10 days, even with presolubilization. It was also observed that the fluidized-bed system was able to accept abrupt increases of loading without a corresponding buildup of excessive organic acids. © ASCE

BIOMECHANICS OF STANDING LONG JUMP WITH HADNHELD WEIGHT

INTRODUCTION: Many studies had proved that extra weights was held in the hands of the athletes during the long jump competition(Minetti &Ardigo 2002; Lenoir, Clercq & Laporte, 2005), and some researchers found that extra weights would increase the jump distance, but those studies did not point out the joint moment and power. The purpose of this study was to investigate the biomechanical difference between unloaded and loaded groups, and to understand the joint moment and power of standing long jump